Display device, display unit, and display system

ABSTRACT

Provided is a display device or a display system capable of displaying images along a curved surface, a display device or a display system capable of displaying images seamlessly in the form of a ring, or a display device or a display system that is suitable for increasing in size. The display device includes a display panel. The display panel includes a first part and a second part and is flexible. The first part can display images. The second part can transmit visible light. The display panel is curved so that the second part and the first part overlap with each other.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/935,130, filed Mar. 26, 2018, now allowed, which is a continuation ofU.S. application Ser. No. 14/994,335, filed Jan. 13, 2016, now U.S. Pat.No. 9,940,086, which claims the benefit of foreign priority applicationsfiled in Japan as Serial No. 2015-009453 on Jan. 21, 2015, and SerialNo. 2015-040295 on Mar. 2, 2015, all of which are incorporated byreference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

One embodiment of the present invention relates to a display device fordisplaying images.

Note that one embodiment of the present invention should not limitedthis technical field. Examples of the technical field of one embodimentof the present invention disclosed in this specification include asemiconductor device, a display device, a light-emitting device, alighting device, a power storage device, a storage device, a method fordriving any of them, and a method for manufacturing any of them.

2. Description of the Related Art

In recent years, it has been required to increase display devices insize and type. Examples include a television device for home use (alsoreferred to as a TV or a television receiver), digital signage, and apublic information display (PID). Larger digital signage, PID, and thelike provide the increased amount of information, and attract moreattention when used for advertisement or the like, so that theeffectiveness of the advertisement is expected to be increased.

Examples of the display device include, typically, a light-emittingdevice including a light-emitting element such as an organicelectroluminescent (EL) element or a light-emitting diode (LED), aliquid crystal display device, and an electronic paper performingdisplay by an electrophoretic method or the like.

For example, in a basic structure of an organic EL element, a layercontaining a light-emitting organic compound is provided between a pairof electrodes. Voltage application to the element makes thelight-emitting organic compound to emit light. A display deviceincluding such an organic EL element needs no backlight which isnecessary for liquid crystal display devices and the like; therefore,thin, lightweight, high contrast, and low power consumption displaydevices are obtained.

Patent Document 1 discloses a flexible light-emitting device in which anorganic EL element is used.

REFERENCE Patent Document [Patent Document 1] Japanese Published PatentApplication No. 2014-197522 SUMMARY OF THE INVENTION

An object of one embodiment of the present invention is to provide adisplay device or a display system capable of displaying images along acurved surface. An object of one embodiment of the present invention isto provide a display device or a display system capable of displayingimages seamlessly in the form of a ring. An object of one embodiment ofthe present invention is to provide a display device or a display systemthat is suitable for increasing in size. An object of one embodiment ofthe present invention is to provide a display device or a display systemwhich attracts more attention and has a high advertising effect. Anobject of one embodiment of the present invention is to provide adisplay device or a display system which is easily maintained andcontrolled. An object of one embodiment of the present invention is toprovide a display system with high power feeding efficiency. An objectof one embodiment of the present invention is to provide a novel displaydevice, display unit, display system, or the like.

Note that the descriptions of these objects do not disturb the existenceof other objects. In one embodiment of the present invention, there isno need to achieve all the objects. Objects other than the above objectscan be derived from the description of the specification and like.

One embodiment of the present invention is a display device including adisplay panel. The display panel includes a first part and a second partand is flexible. The first part displays an image. The second parttransmits visible light. The display panel is curved so that the firstpart overlaps with the second part.

Another embodiment of the present invention is a display deviceincluding a first display panel and a second display panel. Each of thefirst display panel and the second display panel includes a first partand a second part. The first display panel and the second display panelare flexible. The first part displays an image. The second parttransmits visible light. At least one of the first display panel and thesecond display panel is curved to overlap with each other. The firstpart of the first display panel and the second part of the seconddisplay panel includes a region overlapping with each other. The firstpart of the second display panel and the second part of the firstdisplay panel includes a region overlapping with each other.

Another embodiment of the present invention is a display deviceincluding a first display panel to an n-th display panel (n is aninteger of 2 or more). Each of the first to n-th display panels includesa first part and a second part and is flexible. The first part candisplay an image. The second part can transmit visible light. The firstto n-th display panels include every two adjacent display panels whichare curved to partly overlap with each other. The first part of a k-thdisplay panel (k is an integer of 1 or more and n−1 or less) to overlapwith the second part of an (k+1)-th display panel. The first part of then-th display panel overlaps with the second part of the first displaypanel.

Another embodiment of the present invention is a display unit includinga display panel and a support. The display panel includes a first partand a second part and is flexible. The first part displays an image. Thesecond part transmits visible light. The support includes a firstsurface having a curved surface and an attachment mechanism on a sideopposite to the first surface. The attachment mechanism fixes thesupport to a frame. The display panel is fixed along the first surfaceof the support. The second part of the display panel partly extendsbeyond the support.

The display unit preferably includes a power receiving device. The powerreceiving device includes a power receiving resonance coil, a powerreceiving coil, a rectifier circuit, a DC-DC converter, and a battery.The power receiving resonance coil induces a high-frequency voltage bymagnetic resonance. The power receiving coil induces a high-frequencyvoltage by electromagnetic induction with the power receiving resonancecoil. The rectifier circuit rectifies the high-frequency voltage inducedby the power receiving coil. The DC-DC converter receives a directcurrent voltage that is output from the rectifier circuit. The batteryfeeds power using the direct current voltage that is output from theDC-DC converter. It is preferable that the DC-DC converter include aninput power detection unit and a voltage conversion unit, the inputpower detection unit be supplied with a first direct voltage, and thevoltage conversion unit convert the first direct voltage into a seconddirect voltage and output it. The input power detection unit includes aload, a first means for detecting a first voltage proportional to thefirst direct-current voltage, and a second means for detecting a secondvoltage proportional to a current generated in the load. The voltageconversion unit includes a switch for controlling a current generated inthe load, and a third means for keeping a ratio of the first voltage andthe second voltage constant by controlling the switch in accordance withthe first voltage and the second voltage.

The display unit preferably includes a flexible printed circuit (FPC)and a driving device. It is preferable that the driving device output afirst signal to the display panel, be fixed to part of the support otherthan the first surface, and be electrically connected to the displaypanel through the FPC.

Another embodiment of the present invention is a display systemincluding n display units described above, the frame, and an outputdevice. The frame includes an arm having a ring shape and a legsupporting the arm. The output device outputs a second signal to thedisplay unit. The display unit is attached to the arm with theattachment mechanism. When a first to an n-th display units are attachedto the arm, the first part of the display panel of a k-th display unit(k is an integer of 1 or more and n−1 or less) preferably overlaps withthe second part of the display panel of a (k+1)-th display unit, and thefirst part of the display panel of the n-th display unit preferablyoverlaps with the second part of the display panel of the first displayunit.

In the display system descried above, the frame preferably includes aplurality of protrusions or depressions each fitting the attachmentmechanism of the display unit and a mechanism for changing the shape ofthe arm between a closed ring shape and an opened ring shape.

In the display system descried above, the output device preferablyoutput the second signal to the display unit wirelessly.

In the display system descried above, the output device preferablyincludes a memory device or a terminal for connecting with an externalmemory device, and obtains information over a network.

According to one embodiment of the present invention, a display deviceor a display system capable of displaying images along the curvedsurface a display device or a display system capable of displayingimages seamlessly in the form of a ring, a display device or a displaysystem that is suitable for increasing in size, a display device or adisplay system which attracts more attention and has a high advertisingeffect, a display device or a display system which is be easilymaintained and controlled, a display system with high power feedingefficiency, or a novel display device, display unit, display system, orthe like is provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1C illustrate a structure example of a display panel and adisplay device according to one embodiment.

FIGS. 2A to 2C illustrate a structure example of a display deviceaccording to one embodiment.

FIGS. 3A and 3B illustrate a structure example of a display deviceaccording to one embodiment.

FIGS. 4A and 4B illustrate a structure example of a display deviceaccording to one embodiment.

FIGS. 5A and 5B illustrate a structure example of a display unitaccording to one embodiment.

FIGS. 6A to 6C illustrate a structure example of a display unitaccording to one embodiment.

FIG. 7 illustrates a structure example of a display system according toone embodiment.

FIG. 8 illustrates a structure example of a frame according to oneembodiment.

FIG. 9 illustrates a structure example of a display system according toone embodiment.

FIG. 10 illustrates a structure example of a display system according toone embodiment.

FIGS. 11A and 11B illustrate a structure example of a display systemaccording to one embodiment.

FIGS. 12A and 12B illustrate a structure example of a display systemaccording to one embodiment.

FIGS. 13A and 13B illustrate a structure example of a display systemaccording to one embodiment.

FIGS. 14A to 14D illustrate a structure example of a display systemaccording to one embodiment.

FIGS. 15A and 15B illustrate a structure example of a display deviceaccording to one embodiment.

FIGS. 16A to 16C illustrate a structure example of a display deviceaccording to one embodiment.

FIGS. 17A and 17B illustrate a structure example of a display deviceaccording to one embodiment.

FIGS. 18A to 18D illustrate a structure example of a display deviceaccording to one embodiment.

FIGS. 19A to 19E illustrate a structure example of a display deviceaccording to one embodiment.

FIGS. 20A to 20C illustrate a structure example of a display panelaccording to one embodiment.

FIGS. 21A to 21C illustrate a structure example of a display panelaccording to one embodiment.

FIGS. 22A to 22C each illustrate a positional relationship betweendisplay panels according to one embodiment.

FIGS. 23A and 23B illustrate a structure example of a display panelaccording to one embodiment.

FIG. 24 illustrates a structure example of a display panel according toone embodiment.

FIG. 25 illustrates a structure example of a display panel according toone embodiment.

FIGS. 26A to 26C illustrate a structure example of a touch panelaccording to one embodiment.

FIGS. 27A and 27B illustrate a structure example of a touch panelaccording to one embodiment.

FIGS. 28A to 28C illustrate a structure example of a touch panelaccording to one embodiment.

FIGS. 29A to 29C illustrate a structure example of a touch panelaccording to one embodiment.

FIGS. 30A to 30D illustrate a structure example of a touch panelaccording to one embodiment.

FIGS. 31A to 31D illustrate a structure example of a touch panelaccording to one embodiment.

FIGS. 32A to 32C illustrate a structure example of a touch panelaccording to one embodiment.

FIGS. 33A to 33F illustrate a structure example of a touch panelaccording to one embodiment.

FIGS. 34A and 34B illustrate a structure example of a power feedingsystem and a power receiving system according to one embodiment.

FIG. 35A to 35D illustrate a structure example of a DC-DC converteraccording to one embodiment.

FIG. 36A to 36D illustrate a structure example of a DC-DC converteraccording to one embodiment.

FIG. 37A to 37C illustrate a structure example of a DC-DC converteraccording to one embodiment.

FIGS. 38A to 38E illustrate application examples of a display device orthe like according to one embodiment.

FIGS. 39A to 39C illustrate application examples of a display device orthe like according to one embodiment.

FIGS. 40A and 40B illustrate application examples of a display device orthe like according to one embodiment.

FIGS. 41A to 41C are photographs of a display device according to oneexample.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments will be described in detail with reference to drawings. Notethat the present invention is not limited to the description below, andit is easily understood by those skilled in the art that various changesand modifications can be made without departing from the spirit andscope of the present invention. Accordingly, the present inventionshould not be interpreted as being limited to the content of theembodiments below.

Note that in the structures of the invention described below, the sameportions or portions having similar functions are denoted by the samereference numerals in different drawings, and description of suchportions is not repeated. Furthermore, the same hatching pattern isapplied to portions having similar functions, and the portions are notdenoted by reference numerals in some cases.

Note that in each drawing described in this specification, the size, thelayer thickness, or the region of each component is exaggerated forclarity in some cases. Therefore, embodiments of the present inventionare not limited to such a scale.

Note that in this specification and the like, ordinal numbers such as“first”, “second”, and the like are used in order to avoid confusionamong components and do not limit the number.

In this specification and the like, unless otherwise described, the term“image” refers to any image which is displayed in a display region of adisplay device or the like, such as a still image, a moving image, or animage including a still image and a moving image.

Embodiment 1

This embodiment describes a display panel, a display device, a displayunit, a display system, and the like which are embodiments of thepresent invention, with reference to drawings.

In one embodiment of the present invention, a plurality of displaypanels is arranged in one or more directions (e.g., in a row or inmatrix), whereby a display device and a display system each having alarge display region are manufactured.

When a plurality of display panels for the display device and displaysystem each having a large display region are used, each display paneldoes not need to be large in size. Therefore, an apparatus formanufacturing the display panel does not need to be increased in size,which leads to space saving. In addition, since an apparatus formanufacturing small- and medium-size display panels can be used, thereis no need to use a novel manufacturing apparatus for increasing thesize of a display device, which leads to a reduction in manufacturingcost. Furthermore, a decrease in yield caused by increasing the size ofa display panel can be suppressed.

A display device and a display system which include a plurality ofdisplay panels have a larger display region and have an effect ofdisplaying more information at a time than those which include onedisplay panel when the display panels have the same size, for example.

However, conventional display panels have a non-display region thatsurrounds a display region. For this reason, when the plurality ofdisplay panels is arranged to unite respective output images to displaya single image, for example, the image appears divided to a user of thedisplay device.

Although narrowing the non-display regions of display panels (usingdisplay panels with narrower frames) prevents the images of the displaypanels from appearing divided, it is difficult to totally remove thenon-display region.

In addition, a smaller non-display region leads to a decrease in thedistance between the edge of the display panel and an element in thedisplay panel, so that the element easily deteriorates by impuritiesentering from the outside of the display panel in some cases.

In view of them, a display device and a display system of embodiments ofthe present invention include a plurality of display panels overlappingwith each other. In every two display panel overlapping with each other,at least a display panel positioned on the display surface side (upperside) includes a region transmitting visible light that is adjacent to adisplay region. In one embodiment of the present invention, a displayregion of a display panel positioned on a lower side and the region thattransmits visible light of the display panel on the upper side overlapwith each other. Therefore, a non-display region between the displayregions of the overlapping two display panels reduced or even removed.As a result, a large-sized display device and display system in which ajoined portion of the display panels is hardly seen by the user areobtained.

In addition, in one embodiment of the present invention, at least partof the non-display region of the display panel positioned on the upperside transmits visible light and thus can overlap with the displayregion of the display panel positioned on the lower side. Furthermore,in one embodiment of the present invention, at least part of thenon-display region of the display panel positioned on the lower side canoverlap with a display region of the display panel positioned on theupper side or a region blocking visible light thereof. It is notnecessary to reduce the areas of these regions because a reduction inthe area of the frame of the display device (a reduction in area excepta display region) is not affected by these regions.

A larger non-display region leads to an increase in the distance betweenthe edge of the display panel and an element in the display panel, sothat the deterioration of the element due to impurities entering fromthe outside of the display panel is suppressed. For example, in the casewhere an organic EL element is used as a display element, as thedistance between the edge of the display panel and the organic ELelement in the display panel increases, impurities such as moisture oroxygen are less likely to enter (or less likely to reach) the organic ELelement from the outside of the display panel. Since a sufficient areaof the non-display region of the display panel is secured in the displaydevice of one embodiment of the present invention, a highly reliablelarge display device and display system are fabricated even when adisplay panel including an organic EL element or the like is used.

In one embodiment of the present invention, a plurality of displaypanels is arranged in a row and every two adjacent display panels partlyoverlap with each other; thus, a region in which the display regions ofthe plurality of display panels form a continuous display region in theform of a band is used as a single display region. In addition, twodisplay panels at both ends partly overlap with each other; accordingly,some or all of the plurality of display panels are curved. In otherwords, a region in which the display regions of the plurality of displaypanels are seamlessly joined in the form of a cylinder is used as asingle display region.

Structure examples are specifically described below.

STRUCTURE EXAMPLE OF DISPLAY PANEL

FIG. 1A is a schematic top view of a display panel 100 which can be usedfor a display device, a display unit, a display system, and the like ofwhich are embodiments of the present invention.

The display panel 100 includes a substrate 111, a substrate 112, adisplay region 101, a driver circuit 102, a wiring 103, and an FPC 104.

Each of the substrate 111 and the substrate 112 preferably hasflexibility, in which case the display panel 100 can be curved so thatthe display region 101 can have a convex or a concave display surface.Alternatively, a curved substrate having rigidity may be used as thesubstrate 111 and/or the substrate 112.

The display region 101 is a region for displaying images. A plurality ofpixels is included in the display region 101 between the substrate 111and the substrate 112.

The driver circuit 102 is a circuit for driving the pixels included inthe display region 101. Although the driver circuit 102 is formed overthe substrate 111 in this non-limiting example, an integrated circuit(IC) chip may be used as the driver circuit 102 to be mounted on thesubstrate 111 or the FPC 104.

The FPC 104 has a function of supplying a signal from the outside to thepixels included in the display region 101 and to the driver circuit 102through the wiring 103.

The display panel 100 includes a region 110 transmitting visible light(hereinafter also simply referred to as region 110). The region 110 isin contact with the display region 101. Specifically, the region 110transmitting visible light is located along part of the outline of thedisplay region 101. In the example shown in FIG. 1A, the region 110transmitting visible light is provided along both the long side and theshort side of the display region 101 which is rectangular. The drivercircuit 102 and the wiring 103 are provided along one long side and oneshort side of the display region 101 and not provided along the otherlong side and the other short side, in which case the region 110transmitting visible light is adjacent to and in contact with thedisplay region 101.

The region 110 transmitting visible light is preferably provided on aside opposite to the side where the FPC 104 is connected so that thedisplay region 101 is provided between the region 110 and the FPC 104 asshown in FIG. 1A. This is because the display panel 100 can be curved sothat the FPC 104 is located on the side opposite to the display surfaceof the display region 101, which will be described in detail.

A region of the display panel 100 where the driver circuit 102, thewiring 103, the FPC 104, and the like are included is referred to as aregion 120 blocking visible light (hereinafter also simply referred toas region 120). Note that in the case where the driver circuit 102, thewiring 103, and the FPC 104 are formed using light-transmittingmaterials and accordingly the region transmits visible light, the regionis regarded as part of the region 110 transmitting visible light.

In FIG. 1A, the substrate 112 is denoted by a dashed line and covers atleast the display region 101. The substrate 112 may partly or entirelycover the driver circuit 102, the wiring 103, the region 110, and thelike. In addition, the substrate 112 is provided to avoid a terminalportion for connecting the FPC 104 and the wiring 103. Note that anopening may be formed in the substrate 112, in which case the openingoverlaps with the terminal portion so that the surface of the terminalportion is exposed from the opening.

Structure Example 1 of Display Device

FIG. 1B shows a structure example of a display device 30 including twodisplay panels 100. In addition, FIG. 2A is a schematic cross-sectionalview taken along section line A1-A2 in FIG. 1B.

Hereinafter, to distinguish the display panels from each other, the samecomponents included in the display panels from each other, or the samecomponents relating to the display panels from each other, letters(e.g., a, b) are added to reference numerals. Unless otherwisespecified, in describing a structure in which a plurality of displaypanels is included, letters are not added when a common part of thedisplay panels or the components is described.

The display device 30 includes a display panel 100 a and a display panel100 b which are joined to form a ring. Each display surface facesoutward and the display device 30 displays images outward.

The display panel 100 a includes a region 110 a transmitting visiblelight, a region 120 a blocking visible light, and a display region 101a. The display panel 100 b includes a region 110 b transmitting visiblelight, a region 120 b blocking visible light, and a display region 101b. Part of the region 110 a transmitting visible light overlaps with thedisplay surface side of the display region 101 b, so that a viewer seesthe image displayed in the display region 101 b partly through theregion 110 a.

An FPC 104 b, a wiring 103 b, and the like are part of the region 120 bblocking visible light and included in the display panel 100 b, and arecovered with the display region 101 a included in the display panel 100a. Thus, in the display device 30, the display region 101 a and thedisplay region 101 b which is partly covered with the region 110 a arejoined seamlessly.

Similarly, part of the region 110 b transmitting visible light andincluded in the display panel 100 b overlaps with the display surface ofthe display region 101 a included in the display panel 100 a. Inaddition, an FPC 104 a, a wiring 103 a, and the like included in thedisplay panel 100 a are covered with the display region 101 b includedin the display panel 100 b. Thus, in the display device 30, the displayregion 101 b and the display region 101 a which is partly covered withthe region 110 b are joined seamlessly.

A display region 31 in the display device 30 is surrounded by a bolddashed line in FIG. 1B. The display region 31 corresponds to the displayregion 101 a and the display region 101 b which are seamlessly joined toform a ring; accordingly, seamless, ring-shaped images are displayed inthe display region 31. When the display device 30 is applied to apillar, for example, a viewer sees a seamless image at any angle to thepillar.

The display device 30 which is one embodiment of the present inventionis characterized by being capable of displaying a 360-degree seamlessimage in the display region 31. Two adjacent display panels 100 arearranged with their respective display regions 101 joined together, andthe joined portion is not perceived by a viewer. As long as the joinedportion is not perceived by a viewer, the two display panels 100 are notnecessarily in contact with each other. For the same reason, there is noneed to fix the two display panels 100 to each other by bonding or thelike.

Therefore, in this specification and the like, the state where a displaypanel “forms a ring” also refers to a state in which the display panelis curved so that part including one end of the display panel overlapswith part including the other end of the display panel or a state inwhich these parts are in contact with each other. Here, a gap or anotherstructure may be provided between the overlapping parts of the displaypanel. In addition, the state in which a plurality of display panels“forms a ring” refers to a state in which the plurality of displaypanels includes one or more regions where part including an end of onedisplay panel and part including an end of the other display panel whichis adjacent to the one display panel overlap or are in contact with eachother. Here, a gap or a structure may be provided between theoverlapping parts of the two adjacent display panels.

Three or more display panels 100 may be used, though two display panels100 are used in FIG. 1B. An increase in the number of display panels 100increases the size of the display region 31 of the display device 30(the circumference of a ring formed of display region) without a changein the size or design of the display panel 100, and there is no limit tothe size of the display region 31 either.

FIG. 1C shows an example in which two sets of two display panels 100forming a ring are stacked vertically.

Specifically, the display device 30 shown in FIG. 1C includes fourdisplay panels (a display panel 100 a, a display panel 100 b, a displaypanel 100 c, and a display panel 100 d).

The positional relationship between the display panel 100 a and thedisplay panel 100 b is similar to that in FIG. 1B. The positionalrelationship between the display panel 100 c and the display panel 100 dis also similar to that in FIG. 1B.

Part of the region 110 a transmitting visible light and included in thedisplay panel 100 a overlaps with the display surface side of a displayregion 101 c included in the display panel 100 c. Furthermore, part ofthe display region 101 a included in the display panel 100 a covers eachpart of a wiring 103 c, a driver circuit 102 c, and the like, which arepart of a region 120 c (not shown) blocking visible light and includedin the display panel 100 c.

Similarly, part of the region 110 b transmitting visible light andincluded in the display panel 100 b overlaps with the display surfaceside of a display region 101 d included in the display panel 100 d.Furthermore, part of the display region 101 b included in the displaypanel 100 b covers each part of a wiring 103 d, a driver circuit 102 d,and the like, which are part of a region 120 d (not shown) blockingvisible light and included in the display panel 100 d.

The two display regions 101 are joined seamlessly in the verticaldirection in the display region 31 of the display device 30 shown inFIG. 1C, and accordingly, images are displayed seamlessly in thevertical direction as well. Furthermore, in the case where the displaydevice 30 is applied to a pillar or the like, an increase in the numberof display panels 100 disposed in the vertical direction extends thedisplay region 31 in the height direction of the pillar, and there is nolimit to the size of the display region 31 either.

Note that the display region 31 of the display device 30 has any one ofvarious shapes, though it has a columnar shape in the non-limitingexample here. For example, the outline of the display region 31 in thecross section can have various shapes, such as a circle, an oval, apolygon, or a rounded polygon. Alternatively, the display region 31 mayhave a cone shape or a pyramidal shape. In addition, the display region31 can have a polyhedron shape, a rounded polyhedron shape, or the likewithout limitation to the pillar and the conic solid.

For example, the display device 30 applied to a pillar or the like inpublic facilities displays advertisements and the like in everydirection to attract more attention, which leads to an increase inadvertising effects.

For displaying images on the surface of a pillar or the like, forexample, there is a method of providing one curved display panel alongthe surface of the pillar or the like. The structure, however, has alimited region for displaying images and thus displays images only in alimited direction. There is another method of disposing a plurality ofdisplay panels along the surface of a pillar or the like; however, inthe method, a joint portion between two display panels causes a seam inan image.

There is another method of using a projection-type imaging device, suchas a projector, to project images onto the surface of a pillar. In orderto display images on the pillar in every direction using the method,however, a plurality of projectors is needed for each pillar. Inaddition, a large space is needed because the projector and the pillarneeds to be distanced several meters (from 2 m to 5 m or more,typically), which is also a problem. Furthermore, there are some otherproblems when a projection-type imaging device is used: the contrast ofa projected image is decreased in a bright environment by the influenceof light reflected from a pillar or the like; the definition of aprojected image is decreased; if an interrupting object exists betweenthe projector and the pillar, the shadow of the interrupting object iscasted on the pillar; and the like. In addition, distortion of aprojected image might be caused depending on the shape of the surface ofthe pillar or positional relationship between the pillar and theprojector.

In contrast, the display device 30 of one embodiment of the presentinvention displays images by itself and is preferably used at home andthe like and even in a location having limited space. In addition, thedisplay device 30 does not have the above-described problems inprinciple, such as image distortion, a decrease in contrast depending onthe brightness of the surroundings, a decrease in definition, reflectionin the projected image, and the like, and thus displays images withextremely high display quality. The display device 30 does not need alight source, such as a lamp, which is necessary for a projection-typeimaging device; thus, power consumption is reduced, there is no dangerof heat generation, and the display device 30 is freed of the need toreplace light sources. Accordingly, the display device 30 of oneembodiment of the present invention can be referred to as a displaydevice with high reliability and a low running cost.

The thickness of each of the plurality of display panels 100 can be, forexample, greater than or equal to 10 μm and less than or equal to 5 mm,preferably greater than or equal to 20 μm and less than or equal to 4mm, further preferably greater than or equal to 30 μm and less than orequal to 3 mm, typically greater than or equal to 40 μm and less than orequal to 1 mm. As the thickness of the display panel 100 becomes small,the display device 30 is made more compact in size. On the other hand,the display panel 100 having too small a thickness might be reduced inmechanical strength. To increase the mechanical strength of the displaypanel 100 without sacrificing the small thickness and weight, forexample, a flexible protection sheet or the like is bonded to each ofthe display panels 100 so that each of the display panels 100 has amoderate thickness of more than or equal to 0.5 mm and less than orequal to 5 mm in total.

The great decrease in thickness of the display panel 100, the use of aflexible member for the display panels 100, or the like allow the weightof the display panels 100 to be extremely small. The weight of thedisplay panel 100 per display surface area of 100 cm² can be more thanor equal to 0.1 g and less than or equal to 50 g, preferably more thanor equal to 0.1 g and less than or equal to 30 g, further preferablymore than or equal to 0.1 g and less than or equal to 10 g, stillfurther preferably more than or equal to 0.1 g and less than or equal to5 g.

Note that the weight of the display panel 100 may denote the weight ofthe display panel 100 itself (i.e., a portion performing a minimumfunction of displaying images, such as a pair of substrates including anelement and the like). The weight of the display panel 100 may furtherinclude the weight of a member for securing the strength of the displaypanel 100 (e.g., a sheet or a frame), the weight of an FPC, a wiring, aconnecter, and the like which are electrically connected to the displaypanel 100. The use of such lightweight display panels 100 allows theweight of the display device 30 to be equal to or less than that of ascreen or the like which is used for the projection-type display device.

The use of a plurality of relatively small display panels 100 for thedisplay device 30 achieves high-yield fabrication. If all the displaypanels 100 are the same in type, the display devices 30 with differentsizes of the display regions 31 are easily fabricated by changing thenumber or arrangement of the display panels 100. As a result, additionof a product category and low-volume production in accordance with theneeds of customers becomes easier. The easy customization depending onfacilities and location is useful particularly in applying the displaydevice 30 to digital signage or the like. In addition, manufacturers canseparately sell the units including the display panel 100 and users cancustomize the size and shape of the display region 31.

The number of pixels (also referred to as screen resolution) in thedisplay region 31 of the display device 30 is the sum of pixels used fordisplaying images in the display regions 101 of the display panels 100.To fabricate the display device 30 with a predetermined number of pixelsin the display region 31, part of the display region 101 of the displaypanel 100 which is located on the other side of the display surface maybe covered with the display region 101 of the display panel 100 on thedisplay surface side, thereby adjusting the number of pixels in thedisplay region 31 of the display device 30. The display device 30 inwhich the number of pixels in the display region 31 meets user's demandand specifications is thus provided.

The above is the description of Structure Example 1.

Modification Examples of Structure Example 1

The display device 30 can be formed using a single display panel 100,though the above-described display device 30 is formed using a pluralityof display panels 100 to have a large display region 31.

FIGS. 3A and 3B show the display device 30 formed using a single displaypanel 100. FIG. 3B shows the display device 30 shown in FIG. 3A which isrotated about 180 degrees. FIG. 16B is a schematic cross-sectional viewtaken along section line B1-B2 in FIG. 3A.

The display panel 100 is curved to form a ring with the display surfacefacing outward. In addition, part of the region 110 transmitting visiblelight, which is along one side of the display region 101, covers part ofthe display region 101 adjacent to the other side of the display region101.

Part of the display region 101 of the display panel 100 covers thewiring 103, the FPC 104, and the like which are included in the region120 blocking visible light.

A single display panel 100 having such a structure displays seamlessimages in the ring-shaped display region 31.

The display device 30 including a single display panel 100 is preferablyapplied to the following compact devices: wearable devices, such as aring-type wearable device, a bangle-type wearable device, a watch-typewearable device, a choker-type wearable device, and a headband-typewearable device; table-top devices, such as a digital photo frame. It isneedless to say that the display device 30 including two or more displaypanels 100 may be applied to these devices.

The above is the description of Modification Example of StructureExample 1.

Structure Example 2

Structure Example 1 describes an example of the display device 30 inwhich the display panel 100 is curved so that the display surface facingoutward can display images outward, whereas Structure Example 2describes another example of the display device 30 in which the displaypanel 100 is curved so that the display surface facing inward candisplay images inward.

In FIG. 4A, each display surface of the two display panels (the displaypanel 100 a and the display panel 100 b in FIG. 1B) faces inward. FIG.16C is a schematic cross-sectional view taken along section line C1-C2in FIG. 4A. In FIG. 4B, each display surface of the four display panels(the display panels 100 a to 100 d in FIG. 1C) faces inward. Thestructure of the overlapping part of the two adjacent display panels 100is similar to that in Structure Example 1 except the curve direction ofthe display panels 100.

Owing to the plurality of display regions 101 disposed seamlessly toform a ring as described above, the display region 31 of the displaydevice 30 displays seamless images inwardly (i.e., to the inside of thering).

It is preferable that a viewer see an image from the inside of thering-shaped display device 30, in which case the viewer sees a360-degree view of the image and feel a highly realistic sensation. Inaddition, there is no seam in the displayed image, which reduces a sensethat the displayed image is a virtual image on the display device 30 andcreates a high sense of immersion in the image. Such a display device 30is thus suitable for the use in virtual reality (VR). When the displaydevice 30 is used for VR, the display device 30 may be provided so thatthe head of a viewer is surrounded by the display region 101 or may havethe display region 101 large enough to let a viewer inside.

In the case where a single large display panel is disposed in front of aviewer and the case where a plurality of display panels is arranged tosurround a viewer, for example, the ends of the display panel(s) and theboundary of two adjacent display panels are visible, which leads to areduction in a sense of reality and immersion. This applies to a headmounted display (HMD) and the like.

In the case where an image is projected along the inside wall using aprojector or the like, the image is projected on the curved surface,which leads to problems such as a blur in the image and a reduction inclarity (definition) or luminance of the image depending on the distancebetween the wall and the projector. However, one embodiment of thepresent invention displays seamless images surrounding viewers at highdefinition and luminance, leading to an enhancement of a sense ofreality and immersion.

A plurality of viewers inside the display device 30 of one embodiment ofthe present invention sees the same image to have a shared experience.For example, the display device 30 is preferably used in amusementfacilities, such as an amusement park and a game arcade. The displaydevice 30 is applied to exhibition in a planetarium, a museum, an artmuseum, a science museum, an aquarium, and the like. The display device30 is also used in simulation facilities of sports, such as wintersports like skiing and marine sports like diving, and in facilities thatsimulate travel to sight-seeing spots, outer space, and the like.

The display device 30 is easily disassembled: the plurality of displaypanels 100 is easily detached to transfer and build on site, whichenables the use in outdoor or indoor events for a limited time.

In addition to the structures shown in FIGS. 4A and 4B, another displaypanel having a flat or curved display surface may be provided to closeone or both of the top opening and the bottom opening. This structuredisplays images in all directions (on the left, right, top, and bottom)of viewers inside, leading to an enhancement of a sense of reality. Inaddition, a chair or the like for viewers may be put inside the displaydevice 30.

The above is the description of Structure Example 2.

Structure Examples of Display Unit

A structure example of a display unit including a display panel, whichis preferably applied to the display devices described above as examplesand a display system described later, will be described below.

FIGS. 5A and 5B show a structure example of a display unit 20. FIG. 5Bshows the display unit 20 in FIG. 5A which is rotated about 180 degrees.

The display unit 20 includes the display panel 100, a support 130, and adriving device 132.

Part of the surface of the support 130 includes a curved surface. Thedisplay panel 100 is fixed along the curved surface. Although thedisplay panel 100 in FIGS. 5A and 5B is fixed to the support 130 so thatthe display surface is curved convexly, it may be fixed to the support130 so that the display surface is curved concavely as in FIGS. 6A and6B.

The support 130 and the display panel 100 are preferably fixeddetachably using an adhesive whose adhesive strength is low enough toallow them to be detached, an adhesive sheet, a double-sided tape, orthe like.

The support 130 has a mechanical strength high enough to hold the shapeof the display panel 100. Materials, such as resin, metal, and alloy,can be used, for example. Resin is preferable because the display unit20 is reduced in weight.

A plastic member may be used so that the surface curvature of thesupport 130 is freely changed, in which case a mode that the support 130has a convex surface as in FIGS. 5A and 5B and the like and a mode thatthe support 130 has a concave surface as in FIGS. 6A and 6B and the likeare interchanged. In addition, in that case, it is preferable that thebonding of the display panel 100 be performed after the support 130 iscurved at a desired curvature because too much of external force is notapplied to the display panel 100.

Part of the end of the support 130 preferably has a surface continuouslycurved from the surface where the display panel 100 is bonded toward theother surface, in which case the display panel 100 is gently curvedalong the support 130 toward the other surface of the support 130 (i.e.,the surface opposite to the surface where the display panel 100 isbonded) and there is no need to bend part of the display panel 100.

The display panel 100 is preferably fixed to the support 130 so that atleast the region 110 transmitting visible light extends beyond thesupport 130. With the structure, when two display units 20 are arranged,the region 110 of one display panel 100 overlaps the display region 101of the other display panel 100 with no physical interference between thesupports 130.

The display panel 100 is preferably fixed to the support 130 so that atleast the region 110 transmitting visible light and part of the displayregion 101 extends beyond the support 130. With the structure, when twodisplay units 20 are arranged, the part of the display region 101 whichextends beyond the support 130 and included in one display panel 100covers the region 120 blocking visible light and included in the otherdisplay panel 100 with no physical interference between the supports130; thus, the two display regions 101 of the display panels 100 areeasily arranged seamlessly.

The support 130 includes an attachment mechanism 131 on a differentportion from the surface where the display panel 100 is fixed. Using theattachment mechanism 131, the support 130 is fixed to a frame 151 whichis described later. The attachment mechanism 131 in FIGS. 5A and 5B andthe like corresponds to part of the support 130 having a claw-likeshape. Without limitation thereon, other modes can be employed as theattachment mechanism 131 as long as the support 130 is fixed to theframe 151, such as a mechanism for fixing the support 130 to the frame150 using a spring, or a structure including a hole in part of thesupport 130 and a screw or the like for fixing the support 130 and theframe 151 via the hole.

In addition, the attachment mechanism 131 preferably includes amechanism for adjusting the position of the support 130 after thesupport 130 is attached to the frame 151, such as a mechanism foradjusting the support 130 in the directions parallel to two orthogonalaxes along the curved surface of the support 130. Alternatively, amechanism for adjusting the support 130 in the following threedirections is preferably included: a direction parallel to an axisperpendicular to the two orthogonal axes in addition to the directionsparallel to the two orthogonal axes. Further preferably, the attachmentmechanism 131 also includes a mechanism for adjusting the rotation angleof the support 130 using the axis perpendicular to the curved surface ofthe support 130 as a rotation axis. The mechanisms adjusts thepositional relationship between the display regions 101 of two adjacentdisplay units 20 if their positional relationship shifts after thedisplay units 20 are fixed to the frame 151, which is described later.Note that such position adjustment mechanisms may be mounted on not theattachment mechanism 131 but the frame 151.

On the side opposite to the side of the support 130 to which the displaypanel 100 is fixed, the driving device 132 is preferably mounted. Notethat there is no positional limitation and the driving device 132 isfixed anywhere except the side of the support 130 to which the displaypanel 100 is fixed. The display panel 100 is curved so that part thereofis located on the back side of the support 130 to be electricallyconnected to the driving device 132 through the FPC 104.

The driving device 132 supplies a signal and potential for driving thedisplay panel 100 through the FPC 104. The driving device 132 preferablyconverts a signal (hereinafter, also referred to as an image signal)containing image data input from an output device 152 which is describedlater into the signal or potential for driving the display panel 100 andsupplies it to the display panel 100. The driving device 132 may beconfigured to output the signal for driving the display panel 100 byitself without being electrically connected to the output device 152, inwhich case the image data is stored in a memory device incorporated inthe driving device 132 or an external memory device (memory medium),such as a flash memory, storing the image data is connected to thedriving device 132, for example.

The driving device 132 may include at least one of an antenna, awireless receiver, a wireless transmitter, a battery, a printed board (acircuit board), and the like. A printed board mounted with an IC, suchas an arithmetic device or a memory device, can be used. In particular,the driving device 132 configured to receive the signal from the outputdevice 152 by wireless communication has a simpler configuration becausea cable is not needed.

The driving device 132 may include a power receiving device 133. Thedisplay unit may include a power receiving device in addition to thedriving device 132, though it is the driving device 132 that includes apower receiving device in the example of this embodiment. A powerreceiving device in Embodiment 5 can be used for example, though thereis no particular limitation thereon. A power receiving device includinga resonance coil, a rectifier circuit, a DC-DC converter, and a battery,and a power receiving device using a magnetic resonance method for powerfeeding can be used as the power receiving device 133, for example.Since the driving device 132 includes the power receiving device, acable for supplying power to the driving devices is not needed, whichleads to simplifying the structure.

Although the driving device 132 in FIG. 5B is mounted on a portionsticking out of the support 130, other structures can be used as long asthe positional relationship between the driving device 132 and thesupport 130 does not shift.

The driving device 132 may be incorporated in the support 130 as shownin FIG. 6C, in which case the FPC 104 is configured to be electricallyconnected to the driving device 132 through an opening in the support130. Alternatively, the surface of the support 130 may be provided witha connector electrically connected to the driving device 132, a cablehaving the connector, or the like, thereto electrically connecting theconnector and the FPC 104.

The above is the description of the structure examples of the displayunit.

Structure Examples of Display System

Structure examples of a display system to which the display unit can beapplied will be described.

FIG. 7 shows a display system 10 including a plurality of display units20 (display units 20 a to 20 l), the frame 151, and the output device152.

FIG. 8 shows an external view of the frame 151 and the output device152. FIG. 9 is a sectional drawing to show the inside of the displaysystem 10 in FIG. 7, in which part of the frame 151 and the like (on thefront side in the diagram) are cut.

As shown in FIG. 8, the frame 151 includes a plurality of ring-shapedarms 151 a and a plurality of legs 151 b supporting the arms 151 a atregular intervals. In the case where the plurality of display unit 20 isthe same in size, two adjacent arms 151 a are preferably disposed at thesame intervals.

As shown in FIG. 8 and FIG. 9, each arm 151 a is configured to fix thesupport 130 with the attachment mechanism 131 of the support 130 of thedisplay unit 20. For example, each arm 151 a has protrusions ordepressions fitting the attachment mechanisms 131. The protrusions ordepressions are preferably disposed accurately at regular intervals,which prevents positional shift between the display regions 101 of twoadjacent display units 20. As described above, each arm 151 a mayinclude a mechanism for adjusting the positional relationship betweenthe frame 151 and the support 130 of the display unit 20.

Each display unit 20 is fixed to the frame 151 detachably so that partof one display panel 100 covers part of another display panel 100adjacent to the one display panel 100 as shown in FIG. 9. Specifically,each display unit 20 is fixed to the frame 151 detachably so that theregion 110 transmitting visible light and included in the one displaypanel 100 covers part of the display region 101 of the other displaypanel 100, and the display region 101 of the other display panel 100overlaps with part of the region 120 blocking visible light and includedin the one display panel 100. The structure displays seamless imagesacross the entire display region of the display system 10.

The display unit 20 can be detached from the frame 151; thus, in thecase where one display unit 20 malfunctions, only the display unit 20 isreplaced easily, which leads to the display system 10 easily maintainedand controlled. Furthermore, since the display panel 100 is detachedfrom the display unit 20, only the display panel 100 is replaced andother components can be reused, which leads to a reduction in cost. Amanufacturer can sell the display unit 20 to a user in various ways:sell the display unit 20 as a whole, sell only the display panel 100 asa replacement part, or recover the display unit 20 to change only thedisplay panel 100 and then resell the display unit 20.

When the display unit 20 is detached from the frame 181 or when thedisplay unit 20 is attached to the frame 151, the display unit 20 to bedetached or attached and the adjacent display units 20 physicallyinterfere with each other sometimes. This is because the display panels100 of the adjacent display units 20 cover the display unit 20 to bedetached or attached. To prevent the physical interference between thedisplay unit 20 to be detached or attached and the display panels of theadjacent display units 20, the display system 10 includes a mechanismfor pushing out the display units 20 toward the display surface sidewhen the display unit 20 is detached or attached. Specifically, it ispreferable that the frame 151 or the support 130 or the attachmentmechanism 131 of each display unit 20 include the mechanisms for pushingout the display units 20 whose display panels 100 cover the display unit20 to be detached or attached.

The case shown in FIG. 7 and the like is described as an example. InFIG. 7, between two display units 20 stacked vertically, the displaypanel 100 of the upper display unit 20 covers the lower display unit 20.In replacing a display unit 20, a plurality of display units 20 at thesame level as the display unit 20 and a plurality of display units 20over the display unit 20 are pushed out at the same time toward thedisplay surface side. In the case where the display panel 100 of thelower display units 20 covers the lower display units 20, a plurality ofdisplay units 20 under the display unit 20 to be replaced is pushed out.

For example, in replacing the display unit 20 a in FIG. 7, the displayunits 20 b, 20 d, and 20 c are pushed out toward the display surfaceside. In replacing the display unit 20 e, the display units 20 f, 20 g,20 h, 20 a, 20 b, 20 c, and 20 d are pushed out toward the displaysurface side.

Although the display system 10 includes the mechanism for pushing outthe display units 20 from the frame 151 to the display surface side inthe example, other mechanisms may be used as long as a display unit 20to be replaced does not interfere with display panels 100 of displayunits 20 adjacent to the display unit 20. For example, a mechanism forsliding along the rim of the frame 151 or a mechanism for temporarilydetaching the display unit 20 from the display panel 100 may beincluded. Alternatively, the display unit 20 may be replaced with theframe 151 opened using a mechanism for opening and closing the frame 151as described later (see FIGS. 12A and 12B and FIGS. 13A and 13B).

The output device 152 outputs an image signal to the driving device 132of each display unit 20.

The output device 152 is preferably configured to transmit and receive asignal by wireless communication, though the output device 152 may beelectrically connected to each driving device 132 by a cable. Inaddition, when the output device 152 is disposed inside the frame 151 asin FIG. 8 and the like, space is saved.

A reproducing device or a recording/reproducing device for a memorymedium such as a flash memory, a Blu-ray Disc, a digital versatile disc(DVD), or the like; or a recording/reproducing device including a memorydevice, such as a hard disk drive (HDD) or a solid state drive (SSD),can be used as the output device 152. Image data stored in the memorydevice is output to each display unit 20 as an image signal.Alternatively, the output device 152 is preferably configured to outputimage data obtained via network to each display unit 20 as the imagesignal, which leads to ease of displaying the latest data; therefore,this configuration is suitable for digital signage or the like. Inaddition, the output device 152 is preferably configured to temporarilystore data in a memory means included in the output device 152, therebybeing capable of displaying images without network connection (offline).

An uncompressed disk recorder (UDR) capable of outputting an image withhigh resolution, e.g., full high-definition image quality (1920×1080pixels), 4K (3840×2160 pixels), or 8K (7680×4320 pixels), withoutcompression is preferably used as the output device 152.

The output device 152 is preferably configured to divide and convertimage data into a plurality of image signals and output it, therebydisplaying one large image in the display region of the display system10. In addition, there is no need to divide the image data before theimage data is input to the output device 152, leading to enhancing thegeneral versatility.

Although three display units 20 are stacked vertically in thenon-limiting structure examples, the number of display units 20 may beone, two, four, or more. In addition, the display units 20 may bestacked zigzag as shown in FIG. 10, though the three display units 20are stacked and aligned in a row in FIG. 7 and the like.

In the case where the display unit 20 including the display region 101having a concave surface as shown in FIGS. 6A and 6B is used, thedisplay unit 20 can be disposed inside the frame 151, and the outputdevice 152 can be disposed outside the frame 151 or at the level lowerthan the frame 151.

Although four display units 20 are arranged along the rim of the frame151 so that the four display panels 100 forms a ring in FIG. 7 and thelike, the number of display panels is not limited thereto. FIG. 11A is aschematic cross-sectional view in which six display units 20 (displayunits 20 a to 20 f) are arranged along the rim of the frame 151 andwhich is taken along the plane parallel to the arm 151 a. In FIG. 11A,six display panels 100 a to 100 f form a ring.

The display system may include a protective member 134 as in FIG. 11B.The protective member 134 is provided outside (on the display surfaceside) the plurality of display units 20 of the display system so as tosurround them. FIG. 11B is an example in which the protective member 134has a cylindrical shape. For the protective member 134 in a regionoverlapping with at least the display region in the display panel, alight-transmitting material is used. The protective member 134 in aregion other than the region overlapping with the display region mayhave a light-blocking property so that a region other than the regionoverlapping with the display region is not visually recognized. As theprotective member 134, a glass plate, a plastic plate, such as anacrylic plate or a polyvinyl chloride plate, or the like can be used. Aplastic plate in the form of a film or a sheet may be used.

A space 135 between the display unit 20 and the protective member 134may be filled with gas such as air or may include resin or the like forbonding the display unit 20 with the protective member 134.

The frame 151 preferably includes an opening and closing mechanism,which enables work inside the frame 151 after the display unit 20 isattached to the frame 151.

FIGS. 12A and 12B are schematic views of the display system 10 in whichthe frame 151 includes the opening and closing mechanism, seen from thedirection parallel to the leg 151 b of the frame 151.

The arm 151 a in FIGS. 12A and 12B includes a hinge 151 c and a notch151 d. Part of the arm 151 a rotates about the hinge 151 c, therebyopening the frame 151, that is, changing the frame 151 from the state inFIG. 12A to the state in FIG. 12B.

Although the hinge 151 c is opposite to the notch 151 d in FIGS. 12A and12B, the positional relationship between the hinge 151 c and the notch151 d shifts, in which case part of the frame 151 can be opened andclosed like a door. In the case where such an opening and closingmechanism is provided, a wheel or the like is preferably attached to theleg 151 b included in a moving portion of the frame 151 to easily changeshapes. Here, the leg 151 b included in a non-moving portion of theframe 151 may be fixed to the ground or the like.

In FIGS. 13A and 13B, the arm 151 a of the frame 151 includes twonotches. With such a structure, part of the frame 151 is detached asshown in the state in FIG. 13B from the state in FIG. 13A.

Although the system for displaying images in the state where a pluralityof display panels forms a ring is described so far, depending on theplace to use the system, the system may be configured to display imagesin the state where a plurality of display panels does not form a ring.In other words, the system may be configured to display images along thecurved surface or the flat surface.

Usage Examples of Display System

Next, usage examples of the display system of one embodiment of thepresent invention are described. FIGS. 14A to 14D are block diagramsshowing the usage examples of the display system.

The display system 10 in FIG. 14A includes the plurality of displayunits 20 attached to the frame 151 and the output device 152. Eachdisplay unit 20 includes the display panel 100 and the driving device132.

The output device 152 outputs an image signal to each driving device 132of the display units 20, thereby displaying an image on each displaypanel 100 of the display units 20. A user can display an image on theplurality of display panels 100 in real time by supplying image data(Data) that the user wants to display to the output device 152. Inaddition, a user can receive broadcasts on the public airwaves or theInternet by a television receiver, a modem, or the like to supply themas image data to the output device 152.

The output device 152 includes a memory device 153 in FIG. 14B. Thememory device 153 stores image data. The output device 152 outputs animage signal in accordance with the image data to display an image oneach display panel 100 of the display units 20. A user can displaydifferent images on the plurality of display panels 100 by updating theimage data stored in the memory device 153 on a regular basis.

The output device 152 is connected to an external memory device 154 inFIG. 14C, in which case the output device 152 reads image data stored inthe external memory device 154 to output an image signal. A user candisplay another image on the plurality of display panels 100 byreplacing the external memory device 154 or updating the image datastored in the external memory device 154.

As the external memory device 154, a memory device which is connected toand disconnected from the output device 152 with a connector, such as anHDD or an SSD; or a memory media, such as a flash memory, a Blu-rayDisc, or a DVD can be used.

FIG. 14D is an example using the Internet 155 and a server 156. Theserver 156 distributes image data to the output device 152 on theInternet 155. In addition, the plurality of display systems 10 isconnected to the Internet 155, so that the sever 156 controls theplurality of display systems 10 as a lump and continuous updates areprovided as well.

Such a usage is particularly effective for displaying the same data onall the plurality of display systems 10: for example, huge commercialfacilities; public facilities, such as an airport or a hospital;vehicles on public transportation, such as a railway or a bus line; aninformation service display operated by a municipality; and achain-style business for wide-ranging store development.

Note that the output device 152 may include the memory device 153 inFIGS. 14C and 14D. If the memory device 153 is provided in FIG. 14C, thedisplay system 10 displays images by itself without the external memorydevice 154. In addition, if the memory device 153 is provided in FIG.14D, the display system 10 displays images by itself without connectionto the Internet 155 (offline).

The display system of one embodiment of the present invention displays aseamless image along the inside or outside of the ring, which allows aviewer to get information from every direction. Furthermore, the displaysystem attracts more attention than a conventional display deviceconfigured to display images on the flat surface. Therefore, the displaysystem of one embodiment of the present invention is particularly usefulwhen used for advertising, providing information in disaster situations,or the like.

The above is the description of the usage examples of the displaysystem.

At least part of this embodiment can be implemented in combination withany of the embodiments described in this specification as appropriate.

Embodiment 2

In this embodiment, structure examples and application examples of adisplay device of one embodiment of the present invention are describedwith reference to drawings.

Structure Example 1

FIG. 15A is a schematic top view of a display panel 200 included in adisplay device of one embodiment of the present invention.

The display panel 200 includes a display region 201, and a region 210transmitting visible light and a region 220 blocking visible light thatare adjacent to the display region 201. Furthermore, the display panel200 is provided with an FPC 212 in the example illustrated in FIG. 15A.

The display region 201 includes a plurality of pixels arranged in matrixand displays an image. One or more display elements are provided in eachpixel. As the display element, typically, a light-emitting element suchas an organic EL element, a liquid crystal element, or the like can beused.

In the region 210, for example, a pair of substrates included in thedisplay panel 200, a sealant for sealing the display element sandwichedbetween the pair of substrates, and the like may be provided. Here, formembers provided in the region 210, materials that transmit visiblelight are used.

In the region 220, for example, a wiring electrically connected to thepixels included in the display region 201 is provided. In addition tothe wiring, driver circuits (such as a scan line driver circuit and asignal line driver circuit) for driving the pixels may be provided.Furthermore, in the region 220, a terminal electrically connected to theFPC 212 (also referred to as a connection terminal), a wiringelectrically connected to the terminal, and the like may be provided.

A display device 50 of one embodiment of the present invention includesa plurality of such display panels 200. FIG. 15B is a schematic top viewof the display device 50 including three display panels.

Hereinafter, to distinguish the display panels from each other, the samecomponents included in the display panels from each other, or the samecomponents relating to the display panels from each other, letters areadded to reference numerals. Unless otherwise specified, “a” is added toreference numerals for a display panel and components placed on thelowest side (the side opposite to the display surface side), and to oneor more display panels and components placed thereover, “b” or lettersafter “b” in alphabetical order are added from the lower side.Furthermore, unless otherwise specified, in describing a structure inwhich a plurality of display panels is included, letters are not addedwhen a common part of the display panels or the components is described.

The display device 50 in FIG. 15B includes a display panel 200 a, adisplay panel 200 b, and a display panel 200 c.

The display panel 200 b is placed so that part of the display panel 200b overlaps an upper side (a display surface side) of the display panel200 a. Specifically, the display panel 200 b is placed so that a region210 b transmitting visible light of the display panel 200 b overlapspart of a display region 201 a of the display panel 200 a, and thedisplay region 201 a of the display panel 200 a and a region 220 bblocking visible light of the display panel 200 b do not overlap eachother.

Furthermore, the display panel 200 c is placed so that part of thedisplay panel 200 c overlaps an upper side (a display surface side) ofthe display panel 200 b. Specifically, the display panel 200 c is placedso that a region 210 c transmitting visible light of the display panel200 c overlaps part of a display region 201 b of the display panel 200b, and the display region 201 b of the display panel 200 b and a region220 c blocking visible light of the display panel 200 c do not overlapeach other.

The region 210 b transmitting visible light overlaps the display region201 a; thus, the whole display region 201 a is visually recognized fromthe display surface side. Similarly, the whole display region 201 b isalso visually recognized from the display surface side when the region210 c overlaps the display region 201 b. Therefore, a region where thedisplay region 201 a, the display region 201 b, and the display region201 c are placed seamlessly (a region surrounded by a bold dashed linein FIG. 15B) can serve as a display region 51 of the display device 50.

Here, the width W of the region 210 in FIG. 15A is greater than or equalto 0.5 mm and less than or equal to 150 mm, preferably greater than orequal to 1 mm and less than or equal to 100 mm, and further preferablygreater than or equal to 2 mm and less than or equal to 50 mm. Theregion 210 serves as a sealing region, and as the width W of the region210 is larger, the distance between an end surface of the display panel200 and the display region 201 can become longer, so that entry of animpurity such as water into the display region 201 from the outside iseffectively suppressed. In particular, in this structure example, theregion 210 is provided adjacent to the display region 201; thus, it isimportant to set the width W of the region 210 at an appropriate value.For example, in the case where an organic EL element is used as thedisplay element, the width W of the region 210 is set to be greater thanor equal to 1 mm, whereby deterioration of the organic EL element iseffectively suppressed. Note that also in a part other than the region210, the distance between the end portion of the display region 201 andthe end surface of the display panel 200 is preferably in the aboverange.

Structure Example 2

In FIG. 15B, the plurality of display panels 200 overlap each other inone direction; however, a plurality of display panels 200 may overlapeach other in two directions of the vertical and horizontal directions.

FIG. 16A shows an example of the display panel 200 in which the shape ofthe region 210 is different from that in FIG. 15A. In the display panel200 in FIG. 16A, the region 210 is placed along adjacent two sides ofthe display region 201.

FIG. 16B is a schematic perspective view of the display device 50 inwhich the display panels 200 in FIG. 16A are arranged two by two in bothvertical and horizontal directions. FIG. 16C is a schematic perspectiveview of the display device 50 when seen from a side opposite to thedisplay surface side.

In FIGS. 16B and 16C, part of the region 210 b of the display panel 200b overlaps a region along a short side of the display region 201 a ofthe display panel 200 a. In addition, part of the region 210 c of thedisplay panel 200 c overlaps a region along a long side of the displayregion 201 a of the display panel 200 a. Moreover, the region 210 d ofthe display panel 200 d overlaps both a region along a long side of thedisplay region 201 b of the display panel 200 b and a region along ashort side of the display region 201 c of the display panel 200 c.

Therefore, as illustrated in FIG. 16B, a region where the display region201 a, the display region 201 b, the display region 201 c, and thedisplay region 201 d are placed seamlessly can serve as the displayregion 51 of the display device 50.

Here, it is preferable that a flexible material be used for the pair ofsubstrates included in the display panel 200 and the display panel 200have flexibility. Thus, as is the case of the display panel 200 a inFIGS. 16B and 16C, part of the display panel 200 a on the FPC 212 a sideis curved when the FPC 212 a and the like are provided on the displaysurface side, whereby the FPC 212 a is placed under the display region201 b of the adjacent display panel 200 b so as to overlap with thedisplay region 201 b, for example. As a result, the FPC 212 a is placedwithout physical interference with the rear surface of the display panel200 b. Furthermore, when the display panel 200 a and the display panel200 b overlap and are bonded to each other, it is not necessary toconsider the thickness of the FPC 212 a; thus, the difference in heightbetween the top surface of the region 210 b of the display panel 200 band the top surface of the display region 201 a of the display panel 200a is reduced. As a result, the end portion over the display region 201 aof the display panel 200 b is prevented from being visually recognized.

Moreover, each display panel 200 has flexibility, whereby the displaypanel 200 b is curved gently so that the top surface of the displayregion 201 b of the display panel 200 b and the top surface of thedisplay region 201 a of the display panel 200 a are equal to each otherin height. Thus, the heights of the display regions can be equal to eachother except in the vicinity of the region where the display panel 200 aand the display panel 200 b overlap each other, so that the displayquality of an image displayed on the display region 51 of the displaydevice 50 is improved.

Although, the relation between the display panel 200 a and the displaypanel 200 b is taken as an example in the above description, the sameapplies to the relation between any two adjacent display panels.

Furthermore, to reduce the step between two adjacent display panels 200,the thickness of the display panel 200 is preferably small. For example,the thickness of the display panel 200 is preferably less than or equalto 1 mm, further preferably less than or equal to 300 μm, still furtherpreferably less than or equal to 100 μm.

FIG. 17A is a schematic top view of the display device 50 in FIGS. 16Band 16C when seen from the display surface side.

Here, when the region 210 of one display panel 200 does not havesufficiently high transmittance with respect to visible light (e.g.,light with a wavelength of greater than or equal to 400 nm and less thanor equal to 700 nm), luminance of a displayed image may be decreaseddepending on the number of display panels 200 overlapping the displayregions 201. For example, in a region A in FIG. 17A, one display panel200 c overlaps the display region 201 a of the display panel 200 a. In aregion B, the two display panels 200 (the display panels 200 c and 200d) overlap the display region 201 b of the display panel 200 b. In aregion C, the three display panels 200 (the display panels 200 b, 200 cand 200 d) overlap the display region 201 a of the display panel 200 a.

In this case, it is preferable that data of the displayed image becorrected so that the gray scale of the pixels is locally increaseddepending on the number of display panels 200 overlapping the displayregions 201. In this manner, a decrease in the display quality of theimage displayed on the display region 51 of the display device 50 issuppressed.

Alternatively, the position of the display panel 200 placed in the upperportion may be shifted, whereby the number of display panels 200overlapping the display regions 201 of the lower display panels 200 isreduced.

In FIG. 17B, the display panel 200 c and the display panel 200 d placedon the display panel 200 a and the display panel 200 b are relativelyshifted in one direction (X direction) by the distance of the width W ofthe region 210. At this time, there are two kinds of regions: a region Din which one display panel 200 overlaps a display region 201 of anotherdisplay panel 200, and a region E in which two display panels 200overlap a display region 201 of another display panel 200.

Note that the display panel may be relatively shifted in a directionperpendicular to the X direction (Y direction).

In the case where the display panel 200 placed in the upper portion isrelatively shifted, the shape of the contour of a region in which thedisplay regions 201 of the display panels 200 are combined is differentfrom a rectangular shape. Thus, in the case where the shape of thedisplay region 51 of the display device 50 is set to a rectangular shapeas illustrated in FIG. 17B, the display device 50 may be driven so thatno image is displayed on the display regions 201 of the display panels200 that are placed outside the display region 51. Here, considering thenumber of pixels in a region where an image is not displayed, morepixels than the number obtained by dividing the number of all the pixelsin the rectangular display region 51 by the number of display panels 200may be provided in the display region 201 of the display panel 200.

Although the distance of relative shift of each display panel 200 is setto an integral multiple of the width W of the region 210 in the aboveexample, the distance is not limited thereto, and may be set asappropriate in consideration of the shape of the display panel 200, theshape of the display region 51 of the display device 50, in which thedisplay panels 200 are combined, and the like.

Cross-sectional Structure Example

FIG. 18A is a schematic cross-sectional view when the two display panels200 are bonded to each other. In FIG. 18A, the FPC 212 a and an FPC 212b are connected to the display panel 200 a and the display panel 200 bon the display surface side, respectively.

Alternatively, as illustrated in FIG. 18B, the FPC 212 a and the FPC 212b may be connected to the display panel 200 a and the display panel 200b on a side opposite to the display surface side, respectively. Withthis structure, the end portion of the display panel 200 a positioned onthe lower side is attached to the rear surface of the display panel 200b; thus, the attachment area and the mechanical strength of the attachedportion are increased.

Alternatively, as illustrated in FIGS. 18C and 18D, a light-transmittingresin layer 231 may be provided to cover the top surfaces of the displaypanel 200 a and the display panel 200 b. Specifically, the resin layer231 is preferably provided to cover the display regions of the displaypanels 200 a and 200 b and a region where the display panel 200 a andthe display panel 200 b overlap.

By providing the resin layer 231 over the plurality of display panels200, the mechanical strength of the display device 50 can be increased.In addition, the resin layer 231 is formed to have a flat surface,whereby the display quality of an image displayed on the display region51 can be increased. For example, when a coating apparatus such as aslit coater, a curtain coater, a gravure coater, a roll coater, or aspin coater is used, the resin layer 231 with high flatness can beformed.

Furthermore, a difference in refractive index between the resin layer231 and the substrate on the display surface side of the display panel200 is preferably less than or equal to 20%, further preferably lessthan or equal to 10%, still further preferably less than or equal to 5%.By using the resin layer 231 having such a refractive index, therefractive index difference between the display panel 200 and the resincan be reduced and light can be efficiently extracted outside. Inaddition, the resin layer 231 with such a refractive index is providedto cover a step portion between the display panel 200 a and the displaypanel 200 b, whereby the step portion is not easily recognized visually,and the display quality of an image displayed on the display region 51of the display device 50 can be increased.

As a material used for the resin layer 231, for example, an organicresin such as an epoxy resin, an aramid resin, an acrylic resin, apolyimide resin, a polyamide resin, or a polyamide-imide resin can beused.

Alternatively, as illustrated in FIGS. 19A and 19B, a protectivesubstrate 232 is preferably provided over the display device 50 with theresin layer 231 provided therebetween. Here, the resin layer 231 mayserve as a bonding layer for bonding the protective substrate 232 to thedisplay device 10. With the protective substrate 232, the surface of thedisplay device 50 is protected, and moreover, the mechanical strength ofthe display device 50 can be increased. For the protective substrate 232in a region overlapping at least the display region 11, alight-transmitting material is used. Furthermore, the protectivesubstrate 232 in a region other than the region overlapping the displayregion 51 may have a light-blocking property not to be visuallyrecognized.

The protective substrate 232 may have a function of a touch panel. Inthe case where the display panel 200 is flexible and can be bent, theprotective substrate 232 is also preferably flexible.

Furthermore, a difference in refractive index between the protectivesubstrate 232 and the substrate on the display surface side of thedisplay panel 200 or the resin layer 231 is preferably less than orequal to 20%, further preferably less than or equal to 10%, stillfurther preferably less than or equal to 5%.

As the protective substrate 232, a plastic substrate that is formed as afilm, for example, a plastic substrate made from polyimide (PI), anaramid, polyethylene terephthalate (PET), polyethersulfone (PES),polyethylene naphthalate (PEN), polycarbonate (PC), nylon,polyetheretherketone (PEEK), polysulfone (PSF), polyetherimide (PEI),polyarylate (PAR), polybutylene terephthalate (PBT), a silicone resin,and the like, or a glass substrate can be used. The protective substrate232 is preferably flexible. The protective substrate 232 includes afiber or the like (e.g., a prepreg). Furthermore, the protectivesubstrate 232 is not limited to the resin film, and a transparentnonwoven fabric formed by processing pulp into a continuous sheet, asheet including an artificial spider's thread fiber containing proteincalled fibroin, a complex in which the transparent nonwoven fabric orthe sheet and a resin are mixed, a stack of a resin film and a nonwovenfabric containing a cellulose fiber whose fiber width is 4 nm or moreand 100 nm or less, or a stack of a resin film and a sheet including anartificial spider's thread fiber may be used.

Alternatively, as illustrated in FIGS. 19C and 19D, a resin layer 233may be provided on a surface opposite to the display surfaces of thedisplay panel 200 a and the display panel 200 b, and a protectivesubstrate 234 may be provided with the resin layer 233 provided betweenthe protective substrate 234 and each of the display panels 200 a and200 b. In this manner, the display panels 200 a and 200 b are sandwichedbetween the two protective substrates, whereby the mechanical strengthof the display device 50 can be further increased. Furthermore, when thethicknesses of the resin layers 231 and 233 are substantially equal toeach other, and for the protective substrates 232 and 234, materialshaving thicknesses which are substantially equal to each other are used,the plurality of display panels 200 is located at the center of thestack. For example, when the stack including the display panel 200 isbent, by locating the display panel 200 at the center in the thicknessdirection, stress in the lateral direction applied to the display panel200 by bending can be relieved, so that damage can be prevented.

As illustrated in FIGS. 19C and 19D, an opening for extracting the FPC212 a is preferably provided in the resin layer 233 and the protectivesubstrate 234, which are located on the rear surface sides of thedisplay panels 200 a and 200 b. At this time, by providing the resinlayer 233 to cover part of the FPC 212 a, the mechanical strength at aconnection portion between the display panel 200 a and the FPC 212 a canbe increased, and defects such as peeling of the FPC 212 a aresuppressed. Similarly, the resin layer 233 is preferably provided tocover part of the FPC 212 b.

Note that the resin layer 233 and the protective substrate 234, whichare provided on the side opposite to the display surface, do notnecessarily have a light-transmitting property, and a material whichabsorbs or reflects visible light may be used. When the resin layers 233and 231, or the protective substrates 234 and 232 have the samematerials, manufacturing cost can be reduced.

As shown in FIG. 19E, a protective substrate 235 may be provided overthe display device 50. Similarly, a protective substrate 236 may beprovided on the surface of the display panel opposite to the displaysurface. The protective substrate 235 is thicker than the protectivesubstrate 232 in FIGS. 19A to 19D. The protective substrate 236 isthicker than the protective substrate 234 in FIGS. 19C and 19D.

As the protective substrate, a glass substrate, a plastic substrate,such as an acrylic substrate or a polyvinyl chloride substrate, or thelike can be used. Alternatively, metal, wood, stone, or the like may beused as the protective substrate. The use of the thick protectivesubstrate can increase the protection of the surface of the displaydevice 50 and the mechanical strength of the display device 50.

For the protective substrate 235 in a region overlapping at least thedisplay region 51, a light-transmitting material is used. Furthermore,the protective substrate 235 in a region other than the regionoverlapping the display region 51 may have a light-blocking property notto be visually recognized.

The protective substrate 236 does not necessarily have alight-transmitting property, and a material which absorbs or reflectsvisible light may be used.

Structure Example of Display Region

Next, a structure example of the display region 201 of the display panel200 is described. FIG. 20A is a schematic top view in which a region Pin FIG. 16A is enlarged, and FIG. 20B is a schematic top view in which aregion Q in FIG. 16A is enlarged.

As illustrated in FIG. 20A, in the display region 201, a plurality ofpixels 241 is arranged in matrix. In the case where the display panel200 which is capable of full color display with three colors of red,blue, and green is formed, the pixel 241 can display any of the threecolors. Alternatively, a pixel which can display white or yellow inaddition to the three colors may be provided. A region including thepixels 241 corresponds to the display region 201.

A wiring 242 a and a wiring 242 b are electrically connected to onepixel 241. The plurality of wirings 242 a each intersects with thewiring 242 b, and is electrically connected to a circuit 243 a. Theplurality of wirings 242 b is electrically connected to a circuit 243 b.One of the circuits 243 a and 243 b can function as a scan line drivercircuit, and the other can function as a signal line driver circuit. Astructure without one of the circuits 243 a and 243 b or both of themmay be employed.

In FIG. 20A, a plurality of wirings 245 electrically connected to thecircuit 243 a or the circuit 243 b is provided. The wiring 245 iselectrically connected to an FPC 223 in an unillustrated region and hasa function of supplying a signal from the outside to the circuits 243 aand 243 b.

In FIG. 20A, a region including the circuit 243 a, the circuit 243 b,and the plurality of wirings 245 corresponds to the region 220 blockingvisible light.

In FIG. 20B, a region outside the pixel 241 provided closest to the endcorresponds to the region 210 transmitting visible light. The region 210does not include the members blocking visible light, such as the pixel241, the wiring 242 a, and the wiring 242 b. Note that in the case wherepart of the pixel 241, the wiring 242 a, or the wiring 242 b transmitsvisible light, the part of the pixel 241, the wiring 242 a, or thewiring 242 b may be provided to extend to the region 210.

Here, the width W of the region 210 indicates the narrowest width of theregion 210 provided in the display panel 200 in some cases. In the casewhere the width W of the display panel 200 varies depending on thepositions, the shortest length can be referred to as the width W. InFIG. 20B, the distance between the pixel 241 and the end surface of thesubstrate (that is, the width W of the region 210) in the verticaldirection is the same as that in the horizontal direction.

FIG. 20C is a schematic cross-sectional view taken along line A1-A2 inFIG. 20B. The display panels 200 include a pair of light-transmittingsubstrates (a substrate 251 and a substrate 252). The substrate 251 andthe substrate 252 are bonded to each other with a bonding layer 253.Here, the substrate on which the pixel 241, the wiring 242 b, and thelike are formed is referred to as the substrate 251.

As illustrated in FIGS. 20B and 20C, in the case where the pixel 241 ispositioned closest to the end of the display region 101, the width W ofthe region 210 transmitting visible light is the distance between theend portion of the substrate 251 or the substrate 252 and the endportion of the pixel 241.

Note that the end portion of the pixel 241 refers to the end portion ofthe member that is positioned closest to the end and blocks visiblelight in the pixel 241. Alternatively, in the case where alight-emitting element including a layer containing a light-emittingorganic compound between a pair of electrodes (also referred to as anorganic EL element) is used as the pixel 241, the end portion of thepixel 241 may be any of the end portion of the lower electrode, the endportion of the layer containing a light-emitting organic compound, andthe end portion of the upper electrode.

FIG. 21A shows the case where the position of the wiring 242 a isdifferent from that in FIG. 20B. FIG. 21B is a schematic cross-sectionalview taken along line B1-B2 in FIG. 21A, and FIG. 21C is a schematiccross-sectional view taken along line C1-C2 in FIG. 21A.

As illustrated in FIGS. 21A to 21C, in the case where the wiring 242 ais positioned closest to the end of the display region 201, the width Wof the region 210 transmitting visible light is the distance between theend portion of the substrate 251 or the substrate 252 and the endportion of the wiring 242 a. In the case where the wiring 242 atransmits visible light, the region 210 may include a region where thewiring 242 a is provided.

Here, in the case where the density of pixels provided in the displayregion 201 of the display panel 200 is high, a portion where pixels arearranged discontinuously may be formed when the two display panels 200are bonded or when there is a change in relative position of the twodisplay panels.

FIG. 22A shows a positional relation between the display region 201 a ofthe display panel 200 a provided on the lower side and the displayregion 201 b of the display panel 200 b provided on the upper side, seenfrom the display surface side. FIG. 22A shows the vicinities of thecorner portions of the display regions 201 a and 201 b. Part of thedisplay region 201 a is covered with the region 210 b.

FIG. 22A shows an example in which adjacent pixels 241 a and 241 b arerelatively deviated in one direction (Y direction). The arrow in thedrawing denotes a direction in which the display panel 200 a is deviatedfrom the display panel 200 b. FIG. 22B shows an example in which theadjacent pixels 241 a and 241 b are relatively deviated in a verticaldirection and a horizontal direction (X direction and Y direction).

In the examples of FIGS. 22A and 22B, the distances deviated in thevertical direction and the horizontal direction are each shorter thanthe length of one pixel. In this case, image data of the image displayedon either one of the display regions 201 a and 201 b is correcteddepending on the deviation distance, whereby the display quality can bemaintained. Specifically, when the deviation makes the distance betweenthe pixels smaller, the data is corrected so that the gray level(luminance) of the pixels is low, and when the deviation makes thedistance between the pixels larger, the data is corrected so that thegray level (luminance) of the pixels is high. Alternatively, when theone or more pixels overlap, the data is corrected so that the pixelpositioned on a lower side is not driven and the image data is shiftedby one column.

FIG. 22C shows an example in which the pixels 241 a and 241 b, whichshould be adjacent, are relatively deviated in one direction (Ydirection) by a distance of more than one pixel. When the deviation ofmore than one pixel occurs, the pixels are driven so that projectingpixels (pixels which are hatched) are not displayed. Note that the sameapplies to the case where the deviation direction is the X direction.

When the plurality of display panels 200 are bonded, in order tosuppress misalignment, each of the display panels 200 is preferablyprovided with an alignment marker or the like. Alternatively, aprojection and a depression may be formed on the surfaces of the displaypanels 200, and the projection and the depression may be attached toeach other in a region where the two display panels 200 overlap.

At least part of this embodiment can be implemented in combination withany of the embodiments described in this specification as appropriate.

Embodiment 3

In this embodiment, structure examples of a display panel which can beused in a display device, a display unit, and a display system of oneembodiment of the present invention are described with reference todrawings.

Although a display panel mainly including an organic EL element isdescribed in this embodiment as an example, a display panel which can beused in a display device of one embodiment of the present invention isnot limited to this example. A light-emitting panel or a display panelincluding another light-emitting element or display element which willbe described can also be used in a display device of one embodiment ofthe present invention.

FIG. 23A is a plan view of the display panel, and FIG. 23B is an exampleof a cross-sectional view taken along the dashed-dotted line D1-D2 inFIG. 23A. FIG. 23B also shows an example of a cross-sectional view of aregion transmitting visible light 810.

The display panel in Structure Example 1 is a top-emission display panelusing a color filter method. In this embodiment, the display panel canhave a structure in which subpixels of three colors of red (R), green(G), and blue (B), for example, express one color; a structure in whichsubpixels of four colors of R, G, B, and white (W) express one color; astructure in which subpixels of four colors of R, G, B, and yellow (Y)express one color; or the like. There is no particular limitation oncolor elements, and colors other than R, G, B, W, and Y may be used. Forexample, cyan, magenta, or the like may be used.

The display panel shown in FIG. 23A includes the region transmittingvisible light 810, a display portion 804, an operating circuit portion806, and an FPC 808. The region transmitting visible light 810 isadjacent to the display portion 804 and provided along two sides of thedisplay portion 804. The operating circuit portion 806 includes a scanline driver circuit, a signal line driver circuit, and the like. Theregion transmitting visible light 810 includes a region transmittingvisible light. The operation circuit portion 806 includes a regionblocking visible light.

The display panel illustrated in FIG. 23B includes a substrate 701, anadhesive layer 703, an insulating layer 705, a plurality of transistors,a conductive layer 857, an insulating layer 815, an insulating layer816, an insulating layer 817, a plurality of light-emitting elements, aninsulating layer 821, an adhesive layer 822, a coloring layer 845, alight-blocking layer 847, an insulating layer 715, an adhesive layer713, and a substrate 711. The adhesive layer 822, the insulating layer715, the adhesive layer 713, and the substrate 711 transmit visiblelight. Light-emitting elements and transistors included in the displayportion 804 and the operating circuit portion 806 are sealed with theinsulating layer 705, the insulating layer 715, and the adhesive layer822.

The display portion 804 includes a transistor 820 and a light-emittingelement 830 over the substrate 701 with the adhesive layer 703 and theinsulating layer 705 provided therebetween. The light-emitting element830 includes a lower electrode 831 over the insulating layer 817, an ELlayer 833 over the lower electrode 831, and an upper electrode 835 overthe EL layer 833. That is, the light-emitting element 830 includes thelower electrode 831, the upper electrode 835, and the EL layer 833provided between the lower electrode 831 and the upper electrode 835.

The lower electrode 831 is electrically connected to a source electrodeor a drain electrode of the transistor 820. An end portion of the lowerelectrode 831 is covered with the insulating layer 821. The lowerelectrode 831 preferably reflects visible light. The upper electrode 835transmits visible light.

In addition, the display portion 804 includes the coloring layer 845overlapping with the light-emitting element 830 and the light-blockinglayer 847 overlapping with the insulating layer 821. The space betweenthe light-emitting element 830 and the coloring layer 845 is filled withthe adhesive layer 822.

The insulating layer 815 and the insulating layer 816 have an effect ofinhibiting diffusion of impurities to a semiconductor included in thetransistors. As the insulating layer 817, an insulating layer having aplanarization function is preferably selected in order to reduce surfaceunevenness due to the transistor.

Note that the insulating layer 815 and/or the insulating layer 816 maybe omitted in a region where a transistor is not provided in the displaypanel. In particular, it is preferable that the insulating layer 815and/or the insulating layer 816 not be formed in the region transmittingvisible light 810 because the transmittance is improved. FIGS. 23A and23B show structures in each of which the insulating layer 815 is notformed in the region transmitting visible light 810. For example,silicon nitride and silicon oxynitride can be used as the insulatinglayer 815 and the insulating layer 816, respectively.

The operating circuit portion 806 includes a plurality of transistorsover the substrate 701 with the adhesive layer 703 and the insulatinglayer 705 provided therebetween. In FIG. 23B, one of transistorsincluded in the operating circuit portion 806 is illustrated.

The insulating layer 705 and the insulating layer 715 are preferablyhighly resistant to moisture, in which case entry of impurities such aswater into the light-emitting element 830 or the transistor 820 can beinhibited, leading to higher reliability of the display panel. When thedisplay panel includes a substrate, the surface of the display panel canbe protected from a physical impact, which is preferable. The substrate701 is bonded to the insulating layer 705 with the adhesive layer 703.The substrate 711 is bonded to the insulating layer 715 with theadhesive layer 713.

The conductive layer 857 is electrically connected to an externalelectrode through which a signal (e.g., a video signal, a clock signal,a start signal, or a reset signal) or a potential from the outside istransmitted to the operating circuit portion 806. Here, an example inwhich the FPC 808 is provided as the external electrode is described. Toprevent an increase in the number of manufacturing steps, the conductivelayer 857 is preferably formed using the same material and the samestep(s) as those of the electrode or the wiring in the display portionor the driver circuit portion. Here, an example is described in whichthe conductive layer 857 is formed using the same material and the samestep(s) as those of the electrodes of the transistor 820.

In the display panel in FIG. 23B, the FPC 808 is positioned over theinsulating layer 715. The connector 825 is connected to the conductivelayer 857 through an opening provided in the insulating layer 715, theadhesive layer 822, the insulating layer 817, the insulating layer 816,and the insulating layer 815. The connector 825 is also connected to theFPC 808. The FPC 808 and the conductive layer 857 are electricallyconnected to each other via the connector 825.

FIG. 24 is a schematic cross-sectional view when using a liquid crystalelement as a display element. In FIG. 24, a liquid crystal element usinga fringe field switching (FFS) mode is used as the display element. Thedisplay panel in FIG. 24 includes a liquid crystal element 860,polarizing plates 861 and 862, a backlight 863, and the like. The liquidcrystal element 860 includes a comb-shaped first electrode 871, a liquidcrystal 872, and a second electrode 873.

FIG. 25 shows an example of a cross-sectional view of a state where twodisplay panels each shown in FIG. 23B are attached to each other with anadhesive layer 723 therebetween. Note that the two display panels may befixed to each other so as to be attachable to and detachable from eachother using an adsorptive layer instead of the adhesive layer 723.

FIG. 25 shows the display region 201 a (corresponding to the displayportion 804 shown in FIG. 23A) and the region blocking visible light 220a (corresponding to the operating circuit portion 806 and the like shownin FIG. 23A) of the lower (rear) display panel and the display region201 b (corresponding to the display portion 804 shown in FIG. 23A) andthe region transmitting visible light 201 b (corresponding to the regiontransmitting visible light 810 shown in FIG. 23A) of the upper (front)display panel. Furthermore, the cross-sectional view shown in FIG. 25shows an example of an overlapping portion (the region 270 in FIG. 14A)where the two display panels 200 a and 200 b described in Embodiment 2overlap with each other.

In FIG. 25, the display panel positioned on the upper side (the displaysurface side) includes the region transmitting visible light 810adjacent to the display portion 804. Furthermore, the display portion804 of the lower display panel and the region transmitting visible light810 of the upper display panel overlap each other. Thus, a non-displayregion between the display regions of the two overlapping display panelscan be reduced and even removed. As a result, a large-sized displaydevice in which a joint portion of the display panels is hardly seen bythe user can be obtained.

In FIG. 25, the adhesive layer 723 transmitting visible light isprovided between the display portion 804 of the lower display panel andthe region transmitting visible light 810 of the upper display panel.The difference in refractive index between the adhesive layer 723 andthe substrate 701 of the upper display panel and/or the substrate 711 ofthe lower display panel is preferably small. Such a structure can reducereflection by the interface due to the difference in refractive index ina stack located over the display portion 804 of the lower display panel.In addition, display unevenness or luminance unevenness of a largedisplay device can be suppressed.

Examples of Materials and Formation Method

Next, materials and the like that can be used for the display panel aredescribed. Note that description of the components already described inthis specification and the like is omitted in some cases.

For each of the substrates, a material such as glass, quartz, an organicresin, a metal, or an alloy can be used. The substrate through whichlight is extracted from the light-emitting element is formed using amaterial which transmits the light.

In particular, a flexible substrate is preferably used. For example, anorganic resin; or glass, a metal, or an alloy that is thin enough tohave flexibility can be used.

An organic resin, which has a specific gravity smaller than that ofglass, is preferably used for the flexible substrate, in which case thedisplay panel can be lightweight as compared with the case where glassis used.

The substrate is preferably formed using a material with high toughness.In that case, a display panel with high impact resistance that is lesslikely to be broken can be provided. For example, when an organic resinsubstrate or a thin metal or alloy substrate is used, the display panelcan be lightweight and unlikely to be broken as compared with the casewhere a glass substrate is used.

A metal material and an alloy material, which have high thermalconductivity, are preferable because they can easily conduct heat to thewhole substrate and accordingly can prevent a local temperature rise inthe display panel. The thickness of a substrate using a metal materialor an alloy material is preferably greater than or equal to 10 μm andless than or equal to 200 μm, further preferably greater than or equalto 20 μm and less than or equal to 50 μm.

There is no particular limitation on a material of the metal substrateor the alloy substrate, but it is preferable to use, for example,aluminum, copper, nickel, or a metal alloy such as an aluminum alloy orstainless steel.

Furthermore, when a material with high thermal emissivity is used forthe substrate, the surface temperature of the display panel can beprevented from rising, leading to inhibition of breakage or a decreasein reliability of the display panel. For example, the substrate may havea stacked-layer structure of a metal substrate and a layer with highthermal emissivity (the layer can be formed using a metal oxide or aceramic material, for example).

As the substrate having flexibility and a light-transmitting property, aplastic substrate that is formed as a film, for example, a plasticsubstrate made from polyimide (PI), an aramid, polyethyleneterephthalate (PET), polyethersulfone (PES), polyethylene naphthalate(PEN), polycarbonate (PC), nylon, polyetheretherketone (PEEK),polysulfone (PSF), polyetherimide (PEI), polyarylate (PAR), polybutyleneterephthalate (PBT), a silicone resin, and the like, or a glasssubstrate can be used. The substrate may include a fiber or the like(e.g., a prepreg). Furthermore, the substrate is not limited to theresin film, and a transparent nonwoven fabric formed by processing pulpinto a continuous sheet, a sheet including an artificial spider's threadfiber containing protein called fibroin, a complex in which thetransparent nonwoven fabric or the sheet and a resin are mixed, a stackof a resin film and a nonwoven fabric containing a cellulose fiber whosefiber width is 4 nm or more and 100 nm or less, or a stack of a resinfilm and a sheet including an artificial spider's thread fiber may beused.

The flexible substrate may have a stacked-layer structure in which ahard coat layer (e.g., a silicon nitride layer) by which a surface ofthe device is protected from damage, a layer for dispersing pressure(e.g., an aramid resin layer), or the like is stacked over a layer ofany of the above-mentioned materials.

The flexible substrate may be formed by stacking a plurality of layers.When a glass layer is used, a barrier property against water and oxygencan be improved and thus a highly reliable display panel can beprovided.

For example, a flexible substrate in which a glass layer, an adhesivelayer, and an organic resin layer are stacked from the side closer to alight-emitting element can be used. The thickness of the glass layer isgreater than or equal to 20 μm and less than or equal to 200 μm,preferably greater than or equal to 25 μm and less than or equal to 100μm. With such a thickness, the glass layer can have both a high barrierproperty against water and oxygen and high flexibility. The thickness ofthe organic resin layer is greater than or equal to 10 μm and less thanor equal to 200 μm, preferably greater than or equal to 20 μm and lessthan or equal to 50 μm. By providing such an organic resin layer,occurrence of a crack or a break in the glass layer can be inhibited andmechanical strength can be improved. With the substrate that includessuch a composite material of a glass material and an organic resin, ahighly reliable flexible display panel can be provided.

Here, a method for forming a flexible display panel is described.

For convenience, a structure including a pixel and a driver circuit, astructure including an optical member such as a color filter, astructure including a touch sensor, or a structure including afunctional member is referred to as an element layer. An element layerincludes a display element, for example, and may include a wiringelectrically connected to a display element or an element such as atransistor used in a pixel or a circuit in addition to the displayelement.

Here, a support provided with an insulating surface over which anelement layer is formed is called a base material.

As a method for forming an element layer over a flexible base material,there are a method in which an element layer is formed directly over abase material, and a method in which an element layer is formed over asupporting base material and has stiffness and then the element layer isseparated from the supporting base material and transferred to the basematerial.

In the case where a material of the base material can withstand heatingtemperature in the process for forming the element layer, it ispreferred that the element layer be formed directly over the basematerial, in which case a manufacturing process can be simplified. Atthis time, the element layer is preferably formed in a state where thebase material is fixed to the supporting base material, in which casethe transfer of the element layer in a device and between devices can beeasy.

In the case of employing the method in which the element layer is formedover the supporting base material and then transferred to the basematerial, first, a separation layer and an insulating layer are stackedover a supporting base material, and then the element layer is formedover the insulating layer. Then, the element layer is separated from thesupporting base material and then transferred to the base material. Atthis time, a material is selected such that separation at an interfacebetween the supporting base material and the separation layer, at aninterface between the separation layer and the insulating layer, or inthe separation layer occurs. With such a method, the element layer canbe formed at temperatures higher than the upper temperature limit of thebase material, which improves the reliability of the display panel.

For example, it is preferable that stacked layers of a layer including ahigh-melting-point metal material, such as tungsten, and a layerincluding an oxide of the metal material be used as the separationlayer, and stacked layers of a plurality of layers as the insulatinglayer, such as a silicon nitride layer and a silicon oxynitride layer beused over the separation layer. By using a high-melting-point metalmaterial, a high-temperature process can be performed to form theelement layer, resulting in high reliability. For example, impuritiescontained in the element layer can be further reduced, and thecrystallinity of a semiconductor or the like included in the elementlayer can be further increased. For the base material, any of the aboveflexible materials can be preferably used.

Examples of the separation include peeling off by application ofmechanical power, removal of the separation layer by etching, orseparation by dripping of a liquid into part of the separation interfaceto penetrate the entire separation interface.

The separation layer is not necessarily provided in the case whereseparation can occur at an interface between the supporting basematerial and the insulating layer. For example, glass may be used as thesupporting base material, an organic resin such as polyimide may be usedas the insulating layer, a separation trigger may be formed by locallyheating part of the organic resin by laser light or the like, andseparation may be performed at an interface between the glass and theinsulating layer. Alternatively, a layer containing a material with highthermal conductivity (e.g., a metal or a semiconductor) may be providedbetween the supporting base material and the insulating layer containingan organic resin, and this layer is heated by current so that separationeasily occurs, and then separation is performed. In this case, theinsulating layer containing an organic resin can also be used as thebase material.

As the adhesive layer, a variety of curable resins such as a reactivecurable resin, a thermosetting resin, an anaerobic resin, and a photocurable resin such as an ultraviolet curable resin can be used. Examplesof such resins include an epoxy resin, an acrylic resin, a siliconeresin, a phenol resin, a polyimide resin, an imide resin, a polyvinylchloride (PVC) resin, a polyvinyl butyral (PVB) resin, an ethylene vinylacetate (EVA) resin, and the like. In particular, a material with lowmoisture permeability, such as an epoxy resin, is preferable.Alternatively, a two-component-mixture-type resin may be used. Furtheralternatively, an adhesive sheet or the like may be used.

Furthermore, the resin may include a drying agent. For example, asubstance which adsorbs moisture by chemical adsorption, such as anoxide of an alkaline earth metal (e.g., calcium oxide or barium oxide),can be used. Alternatively, a substance that adsorbs moisture byphysical adsorption, such as zeolite or silica gel, may be used. Thedrying agent is preferably included, in which case entry of impuritiessuch as moisture into the light-emitting element can be inhibited andthe reliability of the display panel can be improved.

In addition, a filler with a high refractive index or a light scatteringmember is mixed into the resin, in which case the efficiency of lightextraction from the light-emitting element can be improved. For example,titanium oxide, barium oxide, zeolite, zirconium, or the like can beused.

Insulating films with high resistance to moisture are preferably usedfor the insulating layer 705 and the insulating layer 715.Alternatively, the insulating layer 705 and the insulating layer 715preferably have a function of preventing diffusion of impurities to alight-emitting element.

As an insulating film having an excellent moisture-proof property, afilm containing nitrogen and silicon (e.g., a silicon nitride film or asilicon nitride oxide film), a film containing nitrogen and aluminum(e.g., an aluminum nitride film), or the like can be used.Alternatively, a silicon oxide film, a silicon oxynitride film, analuminum oxide film, or the like can be used.

For example, the water vapor transmittance of the insulating film havingan excellent moisture-proof property is lower than or equal to 1×10⁻⁵[g/(m²·day)], preferably lower than or equal to 1×10⁻⁶ [g/(m²·day)],further preferably lower than or equal to 1×10⁻⁷ [g/(m²·day)], stillfurther preferably lower than or equal to 1×10⁻⁸ [g/(m²·day)].

In the display panel, it is necessary that at least one of theinsulating layers 705 and 715, which is on the light-emitting surfaceside, transmit light emitted from the light-emitting element. In thecase where the display panel includes the insulating layers 705 and 715,one of the insulating layers 705 and 715, which transmits light emittedfrom the light-emitting element, preferably has higher averagetransmittance than the other in a wavelength of 400 nm or more and 800nm or less.

The insulating layers 705 and 715 each preferably include oxygen,nitrogen, and silicon. The insulating layers 705 and 715 each preferablyinclude, for example, silicon oxynitride. Moreover, the insulatinglayers 705 and 715 each preferably include silicon nitride or siliconnitride oxide. It is preferable that the insulating layers 705 and 715be each formed using a silicon oxynitride film and a silicon nitridefilm, which are in contact with each other. The silicon oxynitride filmand the silicon nitride film are alternately stacked so that antiphaseinterference occurs more often in a visible region, whereby the stackcan have higher transmittance of light in the visible region.

There is no particular limitation on the structure of the transistor inthe display panel. For example, a forward staggered transistor or aninverted staggered transistor may be used. Furthermore, a top-gatetransistor or a bottom-gate transistor may be used. A semiconductormaterial used for the transistors is not particularly limited, and forexample, silicon, germanium, or an organic semiconductor can be used.Alternatively, an oxide semiconductor containing at least one of indium,gallium, and zinc, such as an In—Ga—Zn-based metal oxide, may be used.

There is no particular limitation on the crystallinity of asemiconductor material used for the transistors, and an amorphoussemiconductor or a semiconductor having crystallinity (amicrocrystalline semiconductor, a polycrystalline semiconductor, asingle-crystal semiconductor, or a semiconductor partly includingcrystal regions) may be used. It is preferable that a semiconductorhaving crystallinity be used, in which case deterioration of thetransistor characteristics can be inhibited.

For stable characteristics of the transistor, a base film is preferablyprovided. The base film can be formed to have a single-layer structureor a stacked-layer structure using an inorganic insulating film such asa silicon oxide film, a silicon nitride film, a silicon oxynitride film,or a silicon nitride oxide film. The base film can be formed by asputtering method, a chemical vapor deposition (CVD) method (e.g., aplasma CVD method, a thermal CVD method, or a metal organic CVD (MOCVD)method), an atomic layer deposition (ALD) method, a coating method, aprinting method, or the like. Note that the base film is not necessarilyprovided. In each of the above structure examples, the insulating layer705 can serve as a base film of the transistor.

As the light-emitting element, a self-luminous element can be used, andan element whose luminance is controlled by current or voltage isincluded in the category of the light-emitting element. For example, alight-emitting diode (LED), an organic EL element, an inorganic ELelement, or the like can be used.

The light-emitting element may have any of a top emission structure, abottom emission structure, and a dual emission structure. A conductivefilm that transmits visible light is used as the electrode through whichlight is extracted. A conductive film that reflects visible light ispreferably used as the electrode through which light is not extracted.

The conductive film that transmits visible light can be formed using,for example, indium oxide, indium tin oxide, indium zinc oxide, zincoxide (ZnO), or zinc oxide to which gallium is added. Alternatively, afilm of a metal material such as gold, silver, platinum, magnesium,nickel, tungsten, chromium, molybdenum, iron, cobalt, copper, palladium,or titanium; an alloy containing any of these metal materials; a nitrideof any of these metal materials (e.g., titanium nitride); or the likecan be formed thin so as to transmit light. Alternatively, a stackedfilm of any of the above materials can be used as the conductive layer.For example, a stacked film of indium tin oxide and an alloy of silverand magnesium is preferably used, in which case conductivity can beincreased. Further alternatively, graphene or the like may be used.

For the conductive film that reflects visible light, for example, ametal material, such as aluminum, gold, platinum, silver, nickel,tungsten, chromium, molybdenum, iron, cobalt, copper, or palladium or analloy including any of these metal materials can be used. Lanthanum,neodymium, germanium, or the like may be added to the metal material orthe alloy. Alternatively, an alloy containing aluminum (an aluminumalloy) such as an alloy of aluminum and titanium, an alloy of aluminumand nickel, or an alloy of aluminum and neodymium may be used.Alternatively, an alloy containing silver such as an alloy of silver andcopper, an alloy of silver and palladium, or an alloy of silver andmagnesium may be used. An alloy of silver and copper is preferablebecause of its high heat resistance. Furthermore, when a metal film or ametal oxide film is stacked in contact with an aluminum film or analuminum alloy film, oxidation can be prevented. Examples of a materialfor the metal film or the metal oxide film are titanium and titaniumoxide. Alternatively, the conductive film having a property oftransmitting visible light and a film containing any of the above metalmaterials may be stacked. For example, a stacked film of silver andindium tin oxide or a stacked film of an alloy of silver and magnesiumand indium tin oxide can be used.

The lower electrode 831 and the upper electrode 835 can be formed of theconductive film that transmits visible light or the conductive film thatreflects visible light.

The electrodes may be formed separately by an evaporation method or asputtering method. Alternatively, a discharging method such as anink-jet method, a printing method such as a screen printing method, or aplating method may be used.

When a voltage higher than the threshold voltage of the light-emittingelement is applied between the lower electrode 831 and the upperelectrode 835, holes are injected to the EL layer 833 from the anodeside and electrons are injected to the EL layer 833 from the cathodeside. The injected electrons and holes are recombined in the EL layer833 and a light-emitting substance contained in the EL layer 833 emitslight.

The EL layer 833 includes at least a light-emitting layer. In additionto the light-emitting layer, the EL layer 833 may further include one ormore layers containing any of a substance with a high hole-injectionproperty, a substance with a high hole-transport property, ahole-blocking material, a substance with a high electron-transportproperty, a substance with a high electron-injection property, asubstance with a bipolar property (a substance with a high electron- andhole-transport property), and the like.

For the EL layer 833, either a low molecular compound or a highmolecular compound can be used, and an inorganic compound may also beused. Each of the layers included in the EL layer 833 can be formed byany of the following methods: an evaporation method (including a vacuumevaporation method), a transfer method, a printing method, an inkjetmethod, a coating method, and the like.

The light-emitting element 830 may contain two or more kinds oflight-emitting substances. Thus, for example, a light-emitting elementthat emits white light can be achieved. For example, a white emissioncan be obtained by selecting light-emitting substances so that two ormore kinds of light-emitting substances emit light of complementarycolors. Alight-emitting substance that emits red (R) light, green (G)light, blue (B) light, yellow (Y) light, or orange (O) light or alight-emitting substance that emits light containing spectral componentsof two or more of R light, G light, and B light can be used, forexample. A light-emitting substance that emits blue light and alight-emitting substance that emits yellow light may be used, forexample. At this time, the emission spectrum of the light-emittingsubstance that emits yellow light preferably contains spectralcomponents of G light and R light. The emission spectrum of thelight-emitting element 830 preferably has two or more peaks in thewavelength range in a visible region (e.g., greater than or equal to 350nm and less than or equal to 750 nm or greater than or equal to 400 nmand less than or equal to 800 nm).

The EL layer 833 may include a plurality of light-emitting layers. Inthe EL layer 833, the plurality of light-emitting layers may be stackedin contact with one another or may be stacked with a separation layerprovided therebetween. The separation layer may be provided between afluorescent layer and a phosphorescent layer, for example.

The separation layer can be provided, for example, to prevent energytransfer by the Dexter mechanism (particularly triplet energy transfer)from a phosphorescent material or the like in an excited state which isgenerated in the phosphorescent layer to a fluorescent material or thelike in the fluorescent layer. The thickness of the separation layer maybe several nanometers. Specifically, the thickness of the separationlayer may be greater than or equal to 0.1 nm and less than or equal to20 nm, greater than or equal to 1 nm and less than or equal to 10 nm, orgreater than or equal to 1 nm and less than or equal to 5 nm. Theseparation layer contains a single material (preferably, a bipolarsubstance) or a plurality of materials (preferably, a hole-transportmaterial and an electron-transport material).

The separation layer may be formed using a material contained in alight-emitting layer in contact with the separation layer. Thisfacilitates the manufacture of the light-emitting element and reducesthe drive voltage. For example, in the case where the phosphorescentlayer includes a host material, an assist material, and a phosphorescentmaterial (guest material), the separation layer may be formed using thehost material and the assist material. In other words, the separationlayer includes a region not containing the phosphorescent material andthe phosphorescent layer includes a region containing the phosphorescentmaterial in the above structure. Accordingly, the separation layer andthe phosphorescent layer can be evaporated separately depending onwhether a phosphorescent material is used or not. With such a structure,the separation layer and the phosphorescent layer can be formed in thesame chamber. Thus, the manufacturing costs can be reduced.

Moreover, the light-emitting element 830 may be a single elementincluding one EL layer or a tandem element in which EL layers arestacked with a charge generation layer provided therebetween.

The light-emitting element is preferably provided between a pair ofinsulating films having an excellent moisture-proof property. In thatcase, entry of an impurity such as moisture into the light-emittingelement can be inhibited, leading to inhibition of a decrease in thereliability of the display panel.

As the insulating layer 815 and the insulating layer 816, for example,an inorganic insulating film such as a silicon oxide film, a siliconoxynitride film, or an aluminum oxide film can be used. Note that theinsulating layer 815 and the insulating layer 816 may be formed usingdifferent materials. As the insulating layer 817 and insulating layers817 a and 817 b, an organic material such as polyimide, acrylic,polyamide, polyimide amide, or a benzocyclobutene-based resin can beused, for example. Alternatively, a low-dielectric constant material (alow-k material) or the like can be used. Furthermore, each insulatinglayer may be formed by stacking a plurality of insulating films.

The insulating layer 821 is formed using an organic insulating materialor an inorganic insulating material. As the resin, for example, apolyimide resin, a polyamide resin, an acrylic resin, a siloxane resin,an epoxy resin, or a phenol resin can be used. It is particularlypreferable that the insulating layer 821 be formed using aphotosensitive resin material to have an opening portion over the lowerelectrode 831 so that a side wall of the insulating layer 821 in theopening portion is formed as an inclined surface with a curvature.

There is no particular limitation on the method for forming theinsulating layer 821; a photolithography method, a sputtering method, anevaporation method, a droplet discharging method (e.g., an inkjetmethod), a printing method (e.g., a screen printing method or an off-setprinting method), or the like may be used.

For example, a conductive layer functioning as an electrode or a wiringof the transistor, an auxiliary electrode of the light-emitting element,or the like, which is used for the display panel, can be formed to havea single-layer structure or a stacked-layer structure using any of metalmaterials such as molybdenum, titanium, chromium, tantalum, tungsten,aluminum, copper, neodymium, and scandium, and an alloy materialcontaining any of these elements. Alternatively, the conductive layermay be formed using a conductive metal oxide. As the conductive metaloxide, indium oxide (e.g., In₂O₃), tin oxide (e.g., SnO₂), zinc oxide(e.g., ZnO), indium tin oxide (e.g., In₂O₃—SnO₂), indium zinc oxide(e.g., In₂O₃—ZnO), or any of these metal oxide materials in whichsilicon oxide is contained can be used.

The coloring layer is a colored layer that transmits light in a specificwavelength range. For example, a color filter for transmitting light ina red, green, blue, or yellow wavelength range can be used. Eachcoloring layer is formed in a desired position with any of variousmaterials by a printing method, an inkjet method, an etching methodusing a photolithography method, or the like. In a white sub-pixel, aresin such as a transparent resin or a white resin may be provided so asto overlap with the light-emitting element.

The light-blocking layer is provided between the adjacent coloringlayers. The light-blocking layer blocks light emitted from an adjacentlight-emitting element to inhibit color mixture between adjacentlight-emitting elements. Here, the coloring layer is provided such thatits end portion overlaps with the light-blocking layer, whereby lightleakage can be reduced. As the light-blocking layer, a material that canblock light from the light-emitting element can be used; for example, ablack matrix is formed using a resin material containing a metalmaterial, pigment, or dye. Note that it is preferable to provide thelight-blocking layer in a region other than the display portion, such asa driver circuit portion, in which case undesired leakage of guidedlight or the like can be inhibited.

Furthermore, an overcoat covering the coloring layer and thelight-blocking layer may be provided. The overcoat can prevent animpurity and the like contained in the coloring layer from beingdiffused into the light-emitting element. The overcoat is formed with amaterial that transmits light emitted from the light-emitting element;for example, an inorganic insulating film such as a silicon nitride filmor a silicon oxide film, an organic insulating film such as an acrylicfilm or a polyimide film can be used, and further, a stacked-layerstructure of an organic insulating film and an inorganic insulating filmmay be employed.

In the case where upper surfaces of the coloring layer and thelight-blocking layer are coated with a material of the adhesive layer, amaterial which has high wettability with respect to the material of theadhesive layer is preferably used as the material of the overcoat. Forexample, an oxide conductive film such as an ITO film or a metal filmsuch as an Ag film which is thin enough to transmit light is preferablyused as the overcoat.

As the connector, any of a variety of anisotropic conductive films(ACF), anisotropic conductive pastes (ACP), and the like can be used.

This embodiment can be combined as appropriate with any of the otherembodiments.

Embodiment 4

In this embodiment, a touch panel that can be used in a display panel ofone embodiment of the present invention will be described with referenceto drawings. Note that the above description can be referred to for thecomponents of the touch panel, which are similar to those of the displaypanel described in the above embodiments. Although a touch panelincluding a light-emitting element is described as an example in thisembodiment, one embodiment of the present invention is not limitedthereto. For example, a touch panel including another element (e.g., adisplay element), the example of which will be described later, can alsobe used in the display panel of one embodiment of the present invention.

Structure Example 1

FIG. 26A is a top view of the touch panel. FIG. 26B is a cross-sectionalview taken along the dashed-dotted line A-B and the dashed-dotted lineC-D in FIG. 26A. FIG. 26C is a cross-sectional view taken along thedashed-dotted line E-F in FIG. 26A.

A touch panel 390 illustrated in FIG. 26A includes a display portion 301(serving also as an input portion), a scan line driver circuit 303 g(1),an imaging pixel driver circuit 303 g(2), an image signal line drivercircuit 303 s(1), and an imaging signal line driver circuit 303 s(2).

The display portion 301 includes a plurality of pixels 302 and aplurality of imaging pixels 308.

The pixel 302 includes a plurality of sub-pixels. Each sub-pixelincludes a light-emitting element and a pixel circuit.

The pixel circuits supplies electric power for driving thelight-emitting element. The pixel circuits are electrically connected towirings through which selection signals are supplied. The pixel circuitsare also electrically connected to wirings through which image signalsare supplied.

The scan line driver circuit 303 g(1) supplies selection signals to thepixels 302.

The image signal line driver circuit 303 s(1) supplies image signals tothe pixels 302.

A touch sensor is formed using the imaging pixels 308. Specifically, theimaging pixels 308 can sense a touch of a finger or the like on thedisplay portion 301.

The imaging pixels 308 include photoelectric conversion elements andimaging pixel circuits.

The imaging pixel circuits drive photoelectric conversion elements. Theimaging pixel circuits are electrically connected to wirings throughwhich control signals are supplied. The imaging pixel circuits are alsoelectrically connected to wirings through which power supply potentialsare supplied.

Examples of the control signal include a signal for selecting an imagingpixel circuit from which a recorded imaging signal is read, a signal forinitializing an imaging pixel circuit, and a signal for determining thetime it takes for an imaging pixel circuit to sense light.

The imaging pixel driver circuit 303 g(2) supplies control signals tothe imaging pixels 308.

The imaging signal line driver circuit 303 s(2) reads out imagingsignals.

As illustrated in FIGS. 26B and 26C, the touch panel 390 includes thesubstrate 701, the adhesive layer 703, the insulating layer 705, thesubstrate 711, the adhesive layer 713, and the insulating layer 715. Thesubstrates 701 and 711 are bonded to each other with an adhesive layer360.

The substrate 701 and the insulating layer 705 are bonded to each otherwith the adhesive layer 703. The substrate 711 and the insulating layer715 are bonded to each other with the adhesive layer 713.

The substrates 701 and 711 are preferably flexible.

The above embodiments can be referred to for materials used for thesubstrates, the adhesive layers, and the insulating layers.

Each of the pixels 302 includes the sub-pixel 302R, a sub-pixel 302G,and a sub-pixel 302B (see FIG. 26C). The sub-pixel 302R includes alight-emitting module 380R, the sub-pixel 302G includes a light-emittingmodule 380G, and the sub-pixel 302B includes a light-emitting module380B.

For example, the sub-pixel 302R includes the light-emitting element 350Rand the pixel circuit. The pixel circuit includes a transistor 302 t forsupplying electric power to the light-emitting element 350R.Furthermore, the light-emitting module 380R includes the light-emittingelement 350R and an optical element (e.g., a coloring layer 367R thattransmits red light).

The light-emitting element 350R includes a lower electrode 351R, an ELlayer 353, and an upper electrode 352, which are stacked in this order(see FIG. 26C).

The EL layer 353 includes a first EL layer 353 a, an intermediate layer354, and a second EL layer 353 b, which are stacked in this order.

Note that a microcavity structure can be provided for the light-emittingmodule 380R so that light with a specific wavelength can be efficientlyextracted. Specifically, an EL layer may be provided between a film thatreflects visible light and a film that partly reflects and partlytransmits visible light, which are provided so that light with aspecific wavelength can be efficiently extracted.

The light-emitting module 380R, for example, includes the adhesive layer360 that is in contact with the light-emitting element 350R and thecoloring layer 367R.

The coloring layer 367R is positioned in a region overlapping with thelight-emitting element 350R. Accordingly, part of light emitted from thelight-emitting element 350R passes through the adhesive layer 360 andthe coloring layer 367R and is emitted to the outside of thelight-emitting module 380R as indicated by an arrow in FIG. 26B or 26C.

The touch panel 390 includes a light-blocking layer 367BM. Thelight-blocking layer 367BM is provided so as to surround the coloringlayer (e.g., the coloring layer 367R).

The touch panel 390 includes an anti-reflective layer 367 p positionedin a region overlapping with the display portion 301. As theanti-reflective layer 367 p, a circular polarizing plate can be used,for example.

The touch panel 390 includes an insulating layer 321. The insulatinglayer 321 covers the transistor 302 t and the like. Note that theinsulating layer 321 can be used as a layer for covering unevennesscaused by the pixel circuits and the imaging pixel circuits. Aninsulating layer on which a layer that can inhibit diffusion ofimpurities to the transistor 302 t and the like is stacked can be usedas the insulating layer 321.

The touch panel 390 includes a partition 328 that overlaps with an endportion of the lower electrode 351R. In addition, a spacer 329 thatcontrols the distance between the substrate 701 and the substrate 711 isprovided on the partition 328.

The image signal line driver circuit 303 s(1) includes a transistor 303t and a capacitor 303 c. Note that the driver circuit can be formed inthe same process and over the same substrate as those of the pixelcircuits. As illustrated in FIG. 26B, the transistor 303 t may include asecond gate 304 over the insulating layer 321. The second gate 304 maybe electrically connected to a gate of the transistor 303 t, ordifferent potentials may be supplied to these gates. Alternatively, ifnecessary, the second gate 304 may be provided for a transistor 308 t,the transistor 302 t, or the like.

The imaging pixels 308 each include a photoelectric conversion element308 p and an imaging pixel circuit. The imaging pixel circuit can senselight received by the photoelectric conversion element 308 p. Theimaging pixel circuit includes the transistor 308 t.

For example, a PIN photodiode can be used as the photoelectricconversion element 308 p.

The touch panel 390 includes a wiring 311 through which a signal issupplied. The wiring 311 is provided with a terminal 319. Note that anFPC 309 through which a signal such as an image signal or asynchronization signal is supplied is electrically connected to theterminal 319. Note that a printed wiring board (PWB) may be attached tothe FPC 309.

Note that transistors such as the transistors 302 t, 303 t, and 308 tcan be formed in the same process. Alternatively, the transistors may beformed in different processes.

Structure Example 2

FIGS. 27A and 27B are perspective views of a touch panel 505A. Note thatFIGS. 27A and 27B illustrate only main components for simplicity. FIG.28A is a cross-sectional view taken along the dashed-dotted line G-H inFIG. 27A.

As illustrated in FIGS. 27A and 27B, the touch panel 505A includes adisplay portion 501, the scan line driver circuit 303 g(1), a touchsensor 595, and the like. Furthermore, the touch panel 505A includes thesubstrate 701, the substrate 711, and a substrate 590.

The touch panel 505A includes a plurality of pixels and a plurality ofwirings 311. The plurality of wirings 311 can supply signals to thepixels. The plurality of wirings 311 are led to a peripheral portion ofthe substrate 701, and part of the plurality of wirings 311 form theterminal 319. The terminal 319 is electrically connected to an FPC509(1).

The touch panel 505A includes the touch sensor 595 and a plurality ofwirings 598. The plurality of wirings 598 are electrically connected tothe touch sensor 595. The plurality of wirings 598 are led to aperipheral portion of the substrate 590, and part of the plurality ofwirings 598 form a terminal. The terminal is electrically connected toan FPC 509(2). Note that in FIG. 27B, electrodes, wirings, and the likeof the touch sensor 595 provided on the back side of the substrate 590(the side facing the substrate 701) are indicated by solid lines forclarity.

As the touch sensor 595, for example, a capacitive touch sensor can beused. Examples of the capacitive touch sensor include a surfacecapacitive touch sensor and a projected capacitive touch sensor. Anexample of using a projected capacitive touch sensor is described here.

Examples of the projected capacitive touch sensor include a selfcapacitive touch sensor and a mutual capacitive touch sensor, whichdiffer mainly in the driving method. The use of a mutual capacitive typeis preferred because multiple points can be sensed simultaneously.

Note that a variety of sensors that can sense the closeness or thecontact of a sensing target such as a finger can be used as the touchsensor 595.

The projected capacitive touch sensor 595 includes electrodes 591 andelectrodes 592. The electrodes 591 are electrically connected to any ofthe plurality of wirings 598, and the electrodes 592 are electricallyconnected to any of the other wirings 598.

The electrodes 592 each have a shape of a plurality of quadranglesarranged in one direction with one corner of a quadrangle connected toone corner of another quadrangle as illustrated in FIGS. 27A and 27B.

The electrodes 591 each have a quadrangular shape and are arranged in adirection intersecting with the direction in which the electrodes 592extend. Note that the plurality of electrodes 591 is not necessarilyarranged in the direction orthogonal to one electrode 592 and may bearranged to intersect with one electrode 592 at an angle of less than 90degrees.

The wiring 594 intersects with the electrode 592. The wiring 594electrically connects two electrodes 591 between which the electrode 592is positioned. The intersecting area of the electrode 592 and the wiring594 is preferably as small as possible. Such a structure allows areduction in the area of a region where the electrodes are not provided,reducing unevenness in transmittance. As a result, unevenness inluminance of light from the touch sensor 595 can be reduced.

Note that the shapes of the electrodes 591 and the electrodes 592 arenot limited to the above-mentioned shapes and can be any of a variety ofshapes. For example, the plurality of electrodes 591 may be provided sothat space between the electrodes 591 are reduced as much as possible,and a plurality of electrodes 592 may be provided with an insulatinglayer sandwiched between the electrodes 591 and the electrodes 592 andmay be spaced apart from each other to form a region not overlappingwith the electrodes 591. In that case, between two adjacent electrodes592, it is preferable to provide a dummy electrode which is electricallyinsulated from these electrodes, whereby the area of a region having adifferent transmittance can be reduced.

Note that a more specific structure example of the touch sensor 595 willbe described later.

As illustrated in FIG. 28A, the touch panel 505A includes the substrate701, the adhesive layer 703, the insulating layer 705, the substrate711, the adhesive layer 713, and the insulating layer 715. Thesubstrates 701 and 711 are bonded to each other with the adhesive layer360.

An adhesive layer 597 bonds the substrate 590 to the substrate 711 sothat the touch sensor 595 overlaps with the display portion 501. Theadhesive layer 597 transmits light.

The electrodes 591 and the electrodes 592 are formed using a conductivematerial that transmits light. As a light-transmitting conductivematerial, a conductive oxide such as indium oxide, indium tin oxide,indium zinc oxide, zinc oxide, or zinc oxide to which gallium is addedcan be used. Note that a film including graphene may be used as well.The film including graphene can be formed, for example, by reducing afilm including graphene oxide. As a reducing method, a method withapplication of heat or the like can be employed.

The resistance of a material used for conductive films such as theelectrodes 591, the electrodes 592, and the wiring 594, i.e., a wiringand an electrode in the touch panel, is preferably low. Examples of thematerial include indium tin oxide, indium zinc oxide, zinc oxide,silver, copper, aluminum, a carbon nanotube, and graphene.Alternatively, a metal nanowire including a number of conductors with anextremely small width (for example, a diameter of several nanometers)may be used. Note that a metal nanowire, a carbon nanotube, graphene, orthe like may be used for an electrode of the display element, e.g., apixel electrode or a common electrode because of its high transmittance.

The electrodes 591 and the electrodes 592 may be formed by depositing alight-transmitting conductive material on the substrate 590 by asputtering method and then removing an unnecessary portion by a varietyof patterning technique such as photolithography.

The electrodes 591 and the electrodes 592 are covered with an insulatinglayer 593. Furthermore, openings reaching the electrodes 591 are formedin the insulating layer 593, and the wiring 594 electrically connectsthe adjacent electrodes 591. A light-transmitting conductive materialcan be favorably used as the wiring 594 because the aperture ratio ofthe touch panel can be increased. Moreover, a material with higherconductivity than the conductivities of the electrodes 591 and theelectrodes 592 can be favorably used for the wiring 594 because electricresistance can be reduced.

Note that an insulating layer covering the insulating layer 593 and thewiring 594 may be provided to protect the touch sensor 595.

Furthermore, a connection layer 599 electrically connects the wirings598 to the FPC 509(2).

The display portion 501 includes a plurality of pixels arranged in amatrix. Each pixel has the same structure as Structure Example 1; thus,description is omitted.

Any of various kinds of transistors can be used in the touch panel. Astructure in the case of using bottom-gate transistors is illustrated inFIGS. 28A and 28B.

For example, a semiconductor layer containing an oxide semiconductor,amorphous silicon, or the like can be used in the transistor 302 t andthe transistor 303 t illustrated in FIG. 28A.

For example, a semiconductor layer containing polycrystalline siliconthat is obtained by crystallization process such as laser annealing canbe used in the transistor 302 t and the transistor 303 t illustrated inFIG. 28B.

A structure in the case of using top-gate transistors is illustrated inFIG. 28C.

For example, a semiconductor layer including polycrystalline silicon, asingle crystal silicon film that is transferred from a single crystalsilicon substrate, or the like can be used in the transistor 302 t andthe transistor 303 t illustrated in FIG. 28C.

Structure Example 3

FIGS. 29A to 29C are cross-sectional views of a touch panel 505B. Thetouch panel 505B described in this embodiment is different from thetouch panel 505A in Structure Example 2 in that received image data isdisplayed on the side where the transistors are provided, that the touchsensor is provided on the substrate 701 side of the display portion, andthat the FPC 509(2) is provided on the same side as the FPC 509(1).Different structures will be described in detail below, and the abovedescription is referred to for the other similar structures.

The coloring layer 367R is positioned in a region overlapping with thelight-emitting element 350R. The light-emitting element 350R illustratedin FIG. 29A emits light to the side where the transistor 302 t isprovided. Accordingly, part of light emitted from the light-emittingelement 350R passes through the coloring layer 367R and is emitted tothe outside of the light-emitting module 380R as indicated by an arrowin FIG. 29A.

The touch panel 505B includes the light-blocking layer 367BM on thelight extraction side. The light-blocking layer 367BM is provided so asto surround the coloring layer (e.g., the coloring layer 367R).

The touch sensor 595 is provided not on the substrate 711 side but onthe substrate 701 side (see FIG. 29A).

The adhesive layer 597 bonds the substrate 590 to the substrate 701 sothat the touch sensor 595 overlaps with the display portion. Theadhesive layer 597 transmits light.

Note that a structure in the case of using bottom-gate transistors inthe display portion 501 is illustrated in FIGS. 29A and 29B.

For example, a semiconductor layer containing an oxide semiconductor,amorphous silicon, or the like can be used in the transistor 302 t andthe transistor 303 t illustrated in FIG. 29A.

For example, a semiconductor layer containing polycrystalline siliconcan be used in the transistor 302 t and the transistor 303 t illustratedin FIG. 29B.

A structure in the case of using top-gate transistors is illustrated inFIG. 29C.

For example, a semiconductor layer containing polycrystalline silicon, asingle crystal silicon film that is transferred, or the like can be usedin the transistor 302 t and the transistor 303 t illustrated in FIG.29C.

Structure Example of Touch Sensor

A more specific structure example of the touch sensor 595 is describedbelow with reference to drawings.

FIG. 30A is a schematic top view of the touch sensor 595. The touchsensor 595 includes a plurality of electrodes 531, a plurality ofelectrodes 532, a plurality of wirings 541, and a plurality of wirings542 over a substrate 590. The substrate 590 is provided with an FPC 550which is electrically connected to each of the plurality of wirings 541and the plurality of wirings 542.

FIG. 30B shows an enlarged view of a region surrounded by a dasheddotted line in FIG. 30A. The electrodes 531 are each in the form of aseries of rhombic electrode patterns aligned in a lateral direction ofthis figure. The rhombic electrode patterns aligned in a line areelectrically connected to each other. The electrodes 532 are also eachin the form of a series of rhombic electrode patterns aligned in alongitudinal direction in this figure and the rhombic electrode patternsaligned in a line are electrically connected. Part of the electrode 531and part of the electrode 532 overlap and intersect with each other. Atthis intersection portion, an insulator is sandwiched in order to avoidan electrical short-circuit between the electrode 531 and the electrode532.

As shown in FIG. 30C, the electrodes 532 may form a plurality ofisland-shape rhombic electrodes 533 and bridge electrodes 534. Theplurality of island-shape rhombic electrodes 533 are aligned in alongitudinal direction in this figure, and two adjacent electrodes 533are electrically connected to each other by the bridge electrode 534.Such a structure makes it possible that the electrodes 533 and theelectrodes 531 can be formed at the same time by processing the sameconductive film. This can prevent variations in the thickness of thesefilms, and can prevent the resistance value and the light transmittanceof each electrode from varying from place to place. Note that althoughthe electrodes 532 include the bridge electrodes 534 here, theelectrodes 531 may have such a structure.

As shown in FIG. 30D, a design in which rhombic electrode patterns ofthe electrodes 531 and 532 shown in FIG. 30B are hollowed out and onlyedges are left may be used. At that time, when the electrodes 531 andthe electrodes 532 are too small in width for the users to see, theelectrodes 531 and the electrodes 532 can be formed using alight-blocking material such as a metal or an alloy, as described later.In addition, either the electrodes 531 or the electrodes 532 shown inFIG. 30D may include the above bridge electrodes 534.

One of the electrodes 531 is electrically connected to one of thewirings 541. One of the electrodes 532 is electrically connected to oneof the wirings 542.

When a touch panel is formed in such a manner that the touch sensor 595is stacked over a display surface of the display panel, alight-transmitting conductive material is preferably used for theelectrodes 531 and the electrodes 532. In the case where alight-transmitting conductive material is used for the electrodes 531and the electrodes 532 and light from the display panel is extractedthrough the electrodes 531 or the electrodes 532, it is preferable thata conductive film containing the same conductive material be arrangedbetween the electrodes 531 and the electrodes 532 as a dummy pattern.Part of a space between the electrodes 531 and the electrodes 532 isfilled with the dummy pattern, which can reduce variation in lighttransmittance. As a result, unevenness in luminance of light transmittedthrough the touch sensor 595 can be reduced.

As a light-transmitting conductive material, a conductive oxide such asindium oxide, indium tin oxide, indium zinc oxide, zinc oxide, or zincoxide to which gallium is added can be used. Note that a film includinggraphene can be used as well. The film including graphene can be formed,for example, by reducing a film containing graphene oxide. As a reducingmethod, a method with application of heat or the like can be employed.

Further, a metal film or an alloy film which is thin enough to have alight-transmitting property can be used. For example, a metal materialsuch as gold, silver, platinum, magnesium, nickel, tungsten, chromium,molybdenum, iron, cobalt, copper, palladium, or titanium, or an alloymaterial containing any of these metal materials can be used.Alternatively, a nitride of the metal material or the alloy material(e.g., titanium nitride), or the like may be used. Alternatively, astacked film in which two or more of conductive films containing theabove materials are stacked may be used.

For the electrodes 531 and the electrodes 532, a conductive film whichis processed to be too thin to see by the users may be used. Such aconductive film is processed into a lattice shape (a mesh shape), forexample, which makes it possible to achieve high conductivity and highvisibility of the display device. It is preferable that the conductivefilm have a portion in which the width is greater than or equal to 30 nmand less than or equal to 100 μm, preferably greater than or equal to 50nm and less than or equal to 50 μm, and further preferably greater thanor equal to 50 nm and less than or equal to 20 μm. In particular, theconductive film having the pattern width of 10 μm or less is extremelydifficult to see by the users, which is preferable.

As examples, enlarged schematic views of part of the electrodes 531 orthe electrodes 532 (part in a ring formed by a dashed-dotted line inFIG. 30B) are shown in FIGS. 31A to 31D. FIG. 31A shows an example ofthe case in which a lattice-shape conductive film 561 is used. Thelattice-shape conductive film 561 is preferably placed so as not tooverlap the display element included in the display device because lightfrom the display device is not blocked. In that case, it is preferablethat the direction of the lattice be provided so as to be the same asthe direction of the display element arrangement and that the pitch ofthe lattice be an integer multiple of the pitch of the display elementarrangement.

FIG. 31B shows an example of a lattice-shape conductive film 562, whichis processed so as to be provided with triangle openings. Such astructure makes it possible to further reduce the resistance comparedwith the structure shown in FIG. 31A.

In addition, a conductive film 563, which has an irregular patternshape, may be used as shown in FIG. 31C. Such a structure can preventgeneration of moiré when overlapping with the display portion of thedisplay device. Note that “moiré” refers to a fringe pattern created bydiffraction or interference when external light or the like passesthrough or external light is reflected by narrow conductive films or thelike spaced uniformly.

Conductive nanowires may be used for the electrodes 531 and theelectrodes 532. FIG. 31D shows an example of the case in which nanowires564 are used. The nanowires 564 are dispersed at appropriate density soas to be in contact with the adjacent nanowires, which can form atwo-dimensional network; therefore, a conductive film with extremelyhigh light-transmitting property can be provided. For example, ananowire which has a mean value of the diameters of greater than orequal to 1 nm and less than or equal to 100 nm, preferably greater thanor equal to 5 nm and less than or equal to 50 nm, further preferablygreater than or equal to 5 nm and less than or equal to 25 nm can beused. As the nanowire 564, a metal nanowire such as an Ag nanowire, a Cunanowire, and an Al nanowire, a carbon nanotube, or the like can beused. In the case of using an Ag nanowire, for example, lighttransmittance of 89% or more and a sheet resistance of 40 ohm/square ormore and 100 ohm/square or less can be achieved.

Although examples in which a plurality of rhombuses are aligned in onedirection are shown in FIG. 30A and the like as top surface shapes ofthe electrodes 531 and the electrodes 532, the shapes of the electrodes531 and the electrodes 532 are not limited thereto and can have varioustop surface shapes such as a belt shape (a rectangular shape), a beltshape having a curve, and a zigzag shape. In addition, although theabove shows the electrodes 531 and the electrodes 532 are arranged to beperpendicular to each other, they are not necessarily arranged to beperpendicular and the angle formed by two of the electrodes may be lessthan 90°.

FIGS. 32A to 32C illustrate examples of the case where electrodes 536and electrodes 537, which have a top surface shape of thin lines, areused instead of the electrodes 531 and the electrodes 532. FIG. 32Ashows an example in which linear electrodes 536 and 537 are arranged soas to form a lattice shape.

FIG. 32B shows an example in which the electrodes 536 and the electrodes537 have a top surface shape of a zigzag shape. As shown in FIG. 32B,the electrodes 536 and the electrodes 537 are arranged so as not tocross the straight-line portions at the centers but so as to place thecenters of the straight-line portions in different positions from eachother; therefore, the length of closely facing parallel parts of theelectrodes 536 and the electrodes 537 can be longer. This is preferablebecause the capacitance between the electrodes can be increased and thesensitivity can be increased. Alternatively, as shown in FIG. 32C, theelectrodes 536 and the electrodes 537 are arranged so as to have adesign in which part of the straight-line portion of a zigzag shape isprojected, which can increase the capacitance between the electrodesbecause the length of the parts facing each other can be longer evenwhen the centers of the straight-line portions are placed in the sameposition.

FIGS. 33A to 33C show enlarged views of a region surrounded by a dasheddotted line in FIG. 32B, and FIGS. 33D to 33F show enlarged views of aregion surrounded by a dashed dotted line in FIG. 32C. In thesedrawings, the electrodes 536, the electrodes 537, and intersectionportions 538 at which the electrodes 536 and the electrodes 537intersect are illustrated. The straight-line portions of the electrodes536 and the electrodes 537 shown in FIGS. 33A and 33D may have aserpentine shape that meanders with angled corners as shown in FIGS. 33Band 33E or may have a serpentine shape that continuously meanders asshown in FIGS. 33C and 33F.

The above is the description of Structure Example of Touch Sensor.

For example, in this specification and the like, a display element, adisplay device which is a device including a display element, alight-emitting element, and a light-emitting device which is a deviceincluding a light-emitting element can employ a variety of modes or caninclude a variety of elements. The display element, the display device,the light-emitting element, or the light-emitting device includes atleast one of an electroluminescent (EL) element (e.g., an EL elementincluding organic and inorganic materials, an organic EL element, or aninorganic EL element), an LED (e.g., a white LED, a red LED, a greenLED, or a blue LED), a transistor (a transistor that emits lightdepending on a current), an electron emitter, a liquid crystal element,electronic ink, an electrophoretic element, a grating light valve (GLV),a plasma display panel (PDP), a display element using micro electromechanical systems (MEMS), a digital micromirror device (DMD), a digitalmicro shutter (DMS), MIRASOL (registered trademark), an interferometricmodulator display (IMOD) element, a MEMS shutter display element, anoptical-interference-type MEMS display element, an electrowettingelement, a piezoelectric ceramic display, a display element including acarbon nanotube, and the like. Other than the above, a display mediumwhose contrast, luminance, reflectance, transmittance, or the like ischanged by an electric or magnetic effect may be included. Examples of adisplay device using an EL element include an EL display. Displaydevices using electron emitters include a field emission display (FED),an SED-type flat panel display (SED: surface-conduction electron-emitterdisplay), and the like. Examples of display devices including liquidcrystal elements include a liquid crystal display (e.g., a transmissiveliquid crystal display, a transflective liquid crystal display, areflective liquid crystal display, a direct-view liquid crystal display,or a projection liquid crystal display). Examples of a display deviceincluding electronic ink, Electronic Liquid Powder (registeredtrademark), or electrophoretic elements include electronic paper. In thecase of a transflective liquid crystal display or a reflective liquidcrystal display, some or all of pixel electrodes function as reflectiveelectrodes. For example, some or all of pixel electrodes are formed tocontain aluminum, silver, or the like. In such a case, a memory circuitsuch as an SRAM can be provided under the reflective electrodes, leadingto lower power consumption. Note that in the case of using an LED,graphene or graphite may be provided under an electrode or a nitridesemiconductor of the LED. Graphene or graphite may be a multilayer filmin which a plurality of layers are stacked. Such provision of grapheneor graphite enables a nitride semiconductor such as an n-type GaNsemiconductor layer including crystals to be easily formed thereover.Furthermore, a p-type GaN semiconductor layer including crystals, or thelike can be provided thereover, and thus the LED can be formed. Notethat an AlN layer may be provided between the n-type GaN semiconductorlayer including crystals and graphene or graphite. The GaN semiconductorlayers included in the LED may be formed by MOCVD. Note that when thegraphene is provided, the GaN semiconductor layers included in the LEDcan also be formed by a sputtering method.

In this specification and the like, an active matrix method in which anactive element is included in a pixel or a passive matrix method inwhich an active element is not included in a pixel can be used, forexample.

In an active matrix method, as an active element (a non-linear element),not only a transistor but also various active elements (non-linearelements) can be used. For example, an MIM (metal insulator metal), aTFD (thin film diode), or the like can also be used. Since such anelement has few numbers of manufacturing steps, manufacturing cost canbe reduced or yield can be improved. Since the size of the element issmall, the aperture ratio can be improved, so that power consumption canbe reduced or higher luminance can be achieved.

As a method other than the active matrix method, the passive matrixmethod in which an active element (a non-linear element) is not used canalso be used. Since an active element (a non-linear element) is notused, the number of manufacturing steps is small, so that manufacturingcost can be reduced or yield can be improved. Since an active element (anon-linear element) is not used, the aperture ratio can be improved, sothat power consumption can be reduced or higher luminance can beachieved, for example.

Note that an example of the case where a variety of display is performedusing the display panel is shown here; however, one embodiment of thepresent invention is not limited thereto. For example, data is notnecessarily displayed. As an example, the display panel may be used as alighting device. By using the display panel as a lighting device, it canbe used as interior lighting having an attractive design. Alternatively,it can be used as lighting with which various directions can beilluminated. Further alternatively, it may be used as a light source,for example, a backlight, a front light, or the like. In other words, itmay be used as a lighting device for the display panel.

At least part of this embodiment can be implemented in combination withany of the embodiments described in this specification as appropriate.

Embodiment 5

A power feeding system capable of feeding power to a battery of thedisplay unit and the like of one embodiment of the present inventionwill be described.

In one embodiment of the present invention, power may be fed to abattery by a method for feeding power to an object (hereinafter, alsoreferred to as a power receiving device) in a state where contact with apower supply source (hereinafter, also referred to as a powertransmitting device) is not made (such a method is also referred to ascontactless power feeding, wireless feeding, or the like). Examples ofthe contactless power feeding include a magnetic resonance method, anelectromagnetic induction method, an electrostatic induction method, andthe like.

In this embodiment, a power feeding system using a magnetic resonancemethod is described as an example. The magnetic resonance method is amethod for forming an energy propagation path by providing resonatorcoupling between resonance coils each of which is provided in a powertransmitting device and a power receiving device. The magnetic resonancemethod has a longer power transmittable distance than other methodscapable of contactless power feeding (e.g., an electromagnetic inductionmethod and an electrostatic induction method).

Here, input impedance of the power receiving device can change dependingon the charge condition of the battery. That is, the input impedance ofthe power receiving device can change dynamically during the powerfeeding. In that case, when output impedance of a power transmittingdevice is constant, an impedance mismatch is inevitably caused. Thus, inthe power feeding by a magnetic resonance method, it may be difficult tomaintain power feeding efficiency at a high level during the powerfeeding.

Thus, the power receiving device of one embodiment of the presentinvention includes a DC-DC converter configured to detect a voltage (aformer voltage) proportional to a direct-current voltage input from theoutside and a voltage (a latter voltage) proportional to a current inputfrom the outside and to hold a ratio of the former voltage and thelatter voltage constant on the basis thereof.

Specifically, in the DC-DC converter included in the power receivingdevice of one embodiment of the present invention, the ratio of thefirst voltage proportional to an input voltage (the first direct-currentvoltage) and the second voltage proportional to an input current (thecurrent generated in the load) is held constant, whereby input impedancecan be kept constant. Furthermore, impedance conversion can be performedin the DC-DC converter. Thus, in the case where a battery to which poweris supplied exists on an output side of the DC-DC converter, inputimpedance of the DC-DC converter can be kept constant regardless of thecharging state of the battery. Accordingly, when power is supplied to apower receiving device including the DC-DC converter and the battery bya magnetic resonance method, power feeding efficiency can be kept highduring the power feeding.

Power Feeding System

FIG. 34A illustrates a configuration example of a power feeding systemwhere power feeding is performed by a magnetic resonance method. Thepower feeding system illustrated in FIG. 34B includes a powertransmitting device 400 and a power receiving device 330 illustrated inFIG. 34A. Further, the power transmitting device 400 includes ahigh-frequency power supply 401, a coil 402 to which a high-frequencyvoltage generated by the high frequency power supply 401 is applied, anda resonance coil 403 in which a high-frequency voltage is induced byelectromagnetic induction with the coil 402. Note that, in the resonancecoil 403, stray capacitance 404 exists between wirings forming theresonance coil 403. Note that as illustrated in FIG. 34A, it ispreferable that the resonance coil 403 be not directly connected toother components.

Power Receiving Device

FIG. 34B is a diagram illustrating a configuration example of a powerreceiving device in which power feeding is performed by a magneticresonance method. A power receiving device 330 illustrated in FIG. 34Bincludes a resonance coil 331 in which a high-frequency voltage isinduced by magnetic resonance, a coil 332 in which a high-frequencyvoltage is induced by electromagnetic induction with the resonance coil331, a rectifier circuit 333 for rectifying the high-frequency voltageinduced by the coil 332, a DC-DC converter 334 to which a direct-currentvoltage output from the rectifier circuit 333 is input, and a battery335 in which power feeding is performed utilizing the direct-currentvoltage output from the DC-DC converter. Note that, in the resonancecoil 331, stray capacitance 336 exists between wirings forming theresonance coil 331.

Note that as illustrated in FIG. 34B, it is preferable that theresonance coil 331 be not directly connected to another component. Ifanother component is directly connected to the resonance coil 331, theseries resistance and capacitance of the resonance coil 331 areincreased. In this case, a Q value of a circuit including the resonancecoil 331 and another component is lower than that of a circuit onlyincluding the resonance coil 331. This is because the configurationwhere the resonance coil 331 is directly connected to another componenthas lower power feeding efficiency than the configuration where theresonance coil 331 is not directly connected to another component.

The DC-DC converter 334 is capable of keeping input impedance constant.Further, the input impedance of the DC-DC converter 334 does not dependon the impedance of the battery 335 which exists on the output side. Inother words, impedance conversion is performed by the DC-DC converter334. Thus, the input impedance of the DC-DC converter 334 also serves asthe input impedance of the power receiving device 330. Accordingly,input impedance of the power receiving device 330 does not vary even inthe case where the impedance of the battery 335 varies in accordancewith the charging state of the battery 335. As a result, power feedingwith high power feeding efficiency is achieved regardless of thecharging state of the battery 335 in the power receiving device 330.

In the power feeding system illustrated in FIG. 34A, the power receivingdevice 330 illustrated in FIG. 34B is used as a power receiving device.Thus, in the power feeding system in FIG. 34A, power feeding can beperformed regardless of variations in input impedance of the powerreceiving device. That is, in the power feeding system illustrated inFIG. 34A, power feeding with high power feeding efficiency can beperformed without a dynamic change in the power feeding condition.

Next, a structure example of a DC-DC converter which can be used as theDC-DC converter 334 is described.

Structure Example of DC-DC Converter

FIG. 35A illustrates a structure example of the DC-DC converter. TheDC-DC converter in FIG. 35A includes an input power detection unit 1000to which a direct-current voltage (V_In) is input and a voltageconversion unit 2000 that converts the direct-current voltage (V_In)into a direct-current voltage (V_Out) and outputs the direct-currentvoltage (V_Out).

FIGS. 35B and 35C each illustrate a configuration example of the inputpower detection unit 1000 in FIG. 35A. The input power detection unit1000 illustrated in FIG. 35B includes a load 1003 whose one end iselectrically connected to a high-potential-side input node and whose theother end is electrically connected to the voltage conversion unit 2000,a means 1001 that detects a voltage (V_1001) proportional to thedirect-current voltage (V_In), and a means 1002 that detects a voltage(V_1002) proportional to a current (I_1003) generated in the load 1003.Note that the voltage (V_1001) detected by the means 1001 and thevoltage (V_1002) detected by the means 1002 are input to the voltageconversion unit 2000. Note that the input power detection unit 1000illustrated in FIG. 35C has the same configuration as the input powerdetection unit 1000 illustrated in FIG. 35B except that one end of theload 1003 is electrically connected to a low-potential-side input node.In one embodiment of the present invention, as illustrated in FIGS. 35Band 35C, the load 1003 included in the input power detection unit 1000is provided so as to be electrically connected to either thehigh-potential-side input node or the low-potential-side input node.

FIG. 35D illustrates a configuration example of the voltage conversionunit 2000 in FIG. 35A. The voltage conversion unit 2000 in FIG. 35Dincludes a switch 2002 that controls a current generated in the load1003 by switching and a means 2001 that controls the switching of theswitch 2002 in accordance with the voltage (V_1001) and the voltage(V_1002).

Note that as the voltage conversion unit 2000 illustrated in FIG. 35D, acircuit including the means 2001 and a voltage conversion circuit suchas a step-up converter, a flyback converter, or an inverting converteris used, and a switch included in the voltage conversion circuit isapplicable to the switch 2002.

In the DC-DC converter illustrated in FIG. 35A, even in the case wherean input voltage (an input direct-current voltage (V_In)) varies, inputimpedance can be kept constant by the control of an input current (thecurrent (I_1003) generated in the load 1003). Specifically, in the DC-DCconverter illustrated in FIGS. 35A to 35D, the current (I_1003)generated in the load 1003 can be controlled by the switching of theswitch 2002. Further the switching of the switch 2002 is controlled bythe means 2001. Here, the means 2001 controls the switching of theswitch 2002 in accordance with the voltage (V_1001) detected by themeans 1001 and the voltage (V_1002) detected by the means 1002. That is,the means 2001 controls the switching of the switch 2002 in accordancewith the voltage (V_1001) proportional to the input voltage and thevoltage (V_1002) proportional to the input current. Thus, in the DC-DCconverter illustrated in FIGS. 35A to 35D, input impedance can be keptconstant by such a design that the ratio of the voltage (V_1001) and thevoltage (V_1002) is held constant by the switching of the switch 2002controlled by the means 2001.

Example of DC-DC Converter

FIG. 36A illustrates an example of a DC-DC converter according to oneembodiment of the present invention. The DC-DC converter illustrated inFIG. 36A includes a load 4 whose one end is electrically connected to ahigh-potential-side input node, a switch 5 whose one end is electricallyconnected to the other end of the load 4, an inductor 6 whose one end isconnected to the other end of the switch 5 and whose the other end iselectrically connected to a high-potential-side output node, and aswitch 7 whose one end is electrically connected to the other end of theswitch 5 and the one end of the inductor 6 and whose the other end iselectrically connected to a low-potential-side input node and alow-potential-side output node (hereinafter this state is also referredto as “grounded”). Note that a resistance load, an inductive load, orthe like can be used as the load 4. Further, a transistor, a relay, orthe like can be used as the switch 5 and the switch 7. Further, an aircore coil, a core coil, or the like can be used as the inductor 6.

Further, the DC-DC converter illustrated in FIG. 36A includes a means 1which detects a voltage (V_1) proportional to an input direct-currentvoltage (V_In), a means 2 which detects a voltage (V_2) proportional toa current (I_4) generated in the load 4, and a means 3 which holds theratio of the voltage (V_1) and the voltage (V_2) constant by controllingswitching of the switch 5 in accordance with the voltage (V_1) and thevoltage (V_2), turns off the switch 7 in a period when the switch 5 isturned on, and turns on the switch 7 in a period when the switch 5 isturned off.

In the DC-DC converter illustrated in FIG. 36A, the current (I_4)generated in the load 4 becomes zero in the period when the switch 5 isturned off; then, the current (I_4) generated in the load 4 increaseswith time in the period following the change of the switch 5 from theoff state to the on state. This is due to self-induction of the inductor6, and an average value of the current (I_4) that is generated in theload 4 and increases with time converges at a constant value. Thus, inthe DC-DC converter illustrated in FIG. 36A, the amount of current to beoutput can be controlled by the switching of the switch 5.

In the DC-DC converter illustrated in FIG. 36A, the switching of theswitch 5 by the means 3 is controlled in accordance with the voltage(V_1) detected by the means 1 and the voltage (V_2) detected by themeans 2. Here, the means 1 is a means which detects a voltageproportional to an input voltage (voltage at an input node) and themeans 2 is a means which detects a voltage proportional to an inputcurrent (current generated in the load 4). Thus, the means 3 controlsthe switching of the switch 5 so as to hold the ratio of the voltage(V_1) and the voltage (V_2) constant, so that input impedance of theDC-DC converter illustrated in FIG. 36A can be kept constant.

In the DC-DC converter illustrated in FIG. 36A, the switch 7 is providedso as to prevent a breakdown of the switch 5. Specifically, in the casewhere the switch 5 changes from an on state to an off state, currentcontinuously flows through the inductor 6 due to self-induction of theinductor 6. If the switch 7 is not provided, a sharp rise or drop in thepotential of the node to which the other end of the switch 5 and the oneend of the inductor 6 are electrically connected may occur when theswitch 5 changes from an on state to an off state. Thus, in that case, ahigh voltage is applied to the switch 5. As a result, the switch 5 maybe broken down. On the other hand, in the DC-DC converter illustrated inFIG. 36A, a current path generated in the inductor 6 can be secured bythe switch 7 turned on. That is, the breakdown of the switch 5 can beprevented.

Specific Example of Means 1

As the means 1, a circuit illustrated in FIG. 36B can be used. Thecircuit illustrated in FIG. 36B includes a resistor 13 whose one end iselectrically connected to the high-potential-side input node and aresistor 14 whose one end is electrically connected to the other end ofthe resistor 13 and whose the other end is grounded. Further, thepotential of a node where the other end of the resistor 13 and the oneend of the resistor 14 are electrically connected to each other is inputto the means 3. That is, the circuit illustrated in FIG. 36B is acircuit which detects the voltage (V_1) proportional to the inputvoltage (V_In) utilizing resistance voltage division and outputs thevoltage (V_1) to the means 3.

Specific Example of Means 2

The circuit illustrated in FIG. 36C can be used as the means 2. Thecircuit illustrated in FIG. 36C includes an instrumentation amplifier 22to which a voltage of the one end of the load 4 is input as anon-inverting input signal and a voltage of the other end of the load 4is input as an inverting input signal. The instrumentation amplifier 22outputs to the means 3 a voltage proportional to a difference betweenthe voltage input to a non-inverting input terminal and the voltageinput to an inverting input terminal. That is, the instrumentationamplifier 22 outputs to the means 3 a voltage proportional to thevoltage applied between both ends of the load 4. Note that since thevoltage applied between the both ends of the load 4 is proportional tothe current (I_4) generated in the load 4, it can also be said that theinstrumentation amplifier 22 outputs the current (I_4) generated in theload 4 to the means 3. That is, in the circuit illustrated in FIG. 36C,the instrumentation amplifier 22 detects the voltage (V_2) proportionalto the current (I_4) generated in the load 4 and outputs the voltage(V_2) to the means 3.

Specific Example of Means 3

The circuit illustrated in FIG. 36D can be used as the means 3. Thecircuit illustrated in FIG. 36D includes an error amplifier 36 to whichthe voltage (V_2) detected by the means 2 and the voltage (V_1) detectedby the means 1 are input as a non-inverting input signal and aninverting input signal, respectively; a triangle wave oscillator 37; acomparator 38 to which a voltage (triangle wave) output from thetriangle wave oscillator 37 and a voltage output from the erroramplifier 36 are input as a non-inverting input signal and an invertinginput signal, respectively; a buffer 39 to which a voltage output fromthe comparator 38 is input and which controls the switching of theswitch 5 by outputting a voltage which has the same phase as that of thevoltage output from the comparator 38; and an inverter 49 which controlsswitching of the switch 7 by outputting a voltage that has a phaseopposite to that of the voltage output from the comparator 38. Note thata configuration in which the switching of the switch 5 is directlycontrolled by the voltage output from the comparator 38 (a configurationin which the buffer 39 is omitted from the means 3 in FIG. 36D) can alsobe employed.

The error amplifier 36 amplifies a difference between the voltage inputto the non-inverting input terminal and the voltage input to theinverting input terminal and outputs the amplified difference. That is,the error amplifier 36 amplifies the difference between the voltage(V_2) and the voltage (V_1) and outputs the amplified difference.

The comparator 38 compares the voltage input to the non-inverting inputterminal and the voltage input to the inverting input terminal, andoutputs a binary voltage. Specifically, a voltage at a high level isoutput in a period where the voltage output from the error amplifier 36is lower than the triangle wave, and a voltage at a low level is outputin a period where the voltage output from the error amplifier 36 ishigher than the triangle wave. That is, the lower the voltage outputfrom the error amplifier 36 is, the higher the duty cycle of the outputsignal of the comparator 38 becomes. The amount of current output fromthe DC-DC converter is determined in accordance with the duty cycle.Specifically, the higher the duty cycle is, the larger the current (thecurrent (I_4) generated in the load 4) output from the DC-DC converterbecomes. That is, the lower the voltage output from the error amplifier36 is, the larger the current (I_4) generated in the load 4 becomes.

Here, the voltage output from the error amplifier 36 changes inaccordance with the voltage (V_1) that is detected by the means 1 and isproportional to the input voltage (V_In) and the voltage (V_2) that isdetected by the means 2 and is proportional to the current (I_4)generated in the load 4. For example, when the input voltage (V_In)becomes higher, the voltage output from the error amplifier 36 islowered. In other words, when the input voltage (V_In) becomes higher,the duty cycle of the output signal of the comparator 38 becomes higher.Accordingly, in the circuit illustrated in FIG. 36D, the duty cycle ofthe output signal of the comparator 38 becomes high when the inputvoltage (V_In) becomes high; thus, the current (I_4) generated in theload 4 also becomes large. In short, in the circuit illustrated in FIG.36D, the value of the current (I_4) generated in the load 4 can bechanged in accordance with the variation in the value of the inputvoltage (V_In). Thus, in the circuit illustrated in FIG. 36D, byadjusting the design condition, the ratio of the voltage (V_1) that isdetected by the means 1 and is proportional to the input voltage and thevoltage (V_2) that is detected by the means 2 and is proportional to thecurrent (I_4) generated in the load 4 can be held constant.

Modification Example of DC-DC Converter

The DC-DC converter illustrated in FIG. 37A has a structure in which theswitch 7 of the DC-DC converter illustrated in FIG. 36A is replaced witha diode 8. The DC-DC converter illustrated in FIG. 37A has the samefunction and effect as those in FIG. 36A.

Note that in the DC-DC converter illustrated in FIG. 37A, the circuitillustrated in FIG. 36B can be used as the means 1, and the circuitillustrated in FIG. 36C can be used as the means 2. Further, the circuitillustrated in FIG. 37B can be used as the means 3. In short, thecircuit illustrated in FIG. 37B has a configuration in which theinverter 49 is omitted from the circuit illustrated in FIG. 36D.

Further, as illustrated in FIG. 37C, a DC-DC converter in which thediode 8 illustrated in FIG. 37A and a diode 9 whose anode iselectrically connected to the other end of the switch 5, the one end ofthe inductor 6, the one end of the switch 7, and a cathode of the diode8, and whose cathode is electrically connected to the other end of theload 4 and the one end of the switch 5 are added to the DC-DC converterillustrated in FIG. 36A may be used. Accordingly, an effect ofsuppressing breakdown of the switch 5 can be enhanced.

A DC-DC converter in which only the diode 8 or 9 is omitted from theDC-DC converter illustrated in FIG. 37C may be used as the DC-DCconverter 334.

At least part of this embodiment can be implemented in combination withany of the embodiments described in this specification as appropriate.

Embodiment 6

Described below are application examples of the display panel, thedisplay device, the display unit, or the display system of oneembodiment of the present invention.

Although the display region is formed along the outer or inner curvedside surface of a column in the non-limiting examples, the displayregion can be applied to 3D objects. The display region 40 is formed onthe side surface of a columnar body having an oval bottom surface inFIG. 38A, a rounded hexagonal bottom surface in FIG. 38B, and a roundedtriangle bottom surface in FIG. 38C. The display region 40 is formed onthe side surface of a cone having a rounded square bottom surface inFIG. 38D and the side surface of a cone in FIG. 38E.

FIGS. 39A to 39C are examples in which the display regions 40 are formedon clothes. The display region 40 is formed on a shirt in FIG. 39A, inwhich case a seamless display region can be formed by fastening thebuttons. The display region 40 is formed on a polo shirt in FIG. 39B, inwhich case a continuous image can be displayed from the front side tothe back side of the polo shirt. The display regions 40 are formedaround a neck and a cuff of a cut and sewn in FIG. 39C.

Note that the display region 40 can be formed on other clothes withoutlimitation thereon: for example, a top, such as a shirt or a blouse; abottom, such as slacks or skirt; and a dress or overalls. The displayregion 40 may also be formed on a muffler, a scarf, a tie, or the like.

When the display region 40 is detached from clothes, only the clothescan be washed so that the display region 40 is prevented from beingdamaged by the washing. Note that in the case where the display region40 is washable, the clothes may be washed without detaching the displayregion 40.

FIG. 40A is an example in which a display region is formed on columns 41and a curved wall 42. The use of a flexible display panel as a displaypanel in a display region allows formation of the display region along acurved surface.

FIG. 40B is a top view of an amusement facility 43 where the ring-shapeddisplay region 40 is used. Visitors 45 can enjoy a 360-degree view ofimages from a stage 44 surrounded by the display region 40. Furthermore,images can be displayed on the surface of a door 46, leading to anenhancement of a sense of reality.

At least one of the display panel 100, the display device 30, thedisplay unit 20, and the display system 10 can be used for the displayregion 40, which are embodiments of the present invention.

At least part of this embodiment can be implemented in combination withany of the embodiments described in this specification as appropriate.

Example

In this example, the display device including a ring-shaped displayregion of one embodiment of the present invention was fabricated.

A display panel used for the display device fabricated in this examplewas formed as follows: over a glass substrate, a tungsten film wasformed first as a separation layer, and then, a layer to be separatedincluding an insulating layer, a transistor, a light-emitting element,and the like was formed over the separation layer. Furthermore, aseparation layer was formed over another glass substrate, and a layer tobe separated including an insulating layer, a coloring layer, alight-blocking layer, and the like was formed over the separation layer.Then, the two substrates were bonded to each other using an adhesivematerial. The layers to be separated were separated from the respectiveglass substrates, and flexible substrates were bonded to the layersusing an adhesive material. In this manner, the display panel wasfabricated.

As the transistor, a transistor including a c-axis aligned crystallineoxide semiconductor (CAAC-OS) was used for a semiconductor layer where achannel is formed. Unlike amorphous semiconductor, the CAAC-OS has fewdefect states, so that the reliability of the transistor can beimproved. Moreover, since the CAAC-OS does not have a grain boundary, astable and uniform film can be formed over a large area, and stress thatis caused by bending a flexible display panel or a display device doesnot easily make a crack in a CAAC-OS film.

A CAAC-OS is a crystalline oxide semiconductor having c-axis alignmentof crystals in a direction substantially perpendicular to the filmsurface. It has been found that oxide semiconductors have a variety ofcrystal structures other than a single-crystal structure. An example ofsuch structures is a nano-crystal (nc) structure, which is an aggregateof nanoscale microcrystals. The crystallinity of a CAAC-OS structure islower than that of a single-crystal structure and higher than that of annc structure.

In this example, a channel-etched transistor including an In—Ga—Zn-basedoxide was used. The transistor was fabricated over a glass substrate ata process temperature lower than 500° C.

As the light-emitting element, a tandem (stack) organic EL elementemitting white light is used. The light-emitting element has a topemission structure, where light generated by the light-emitting elementis extracted to the outside of the display panel through a color filter.

The fabricated display panel had a 13.5-inch-diagonal display portion,1280×720 pixels, a pixel size of 234 μm×234 μm, a resolution of 108 ppi,and an aperture ratio of 61.1%. The display panel had a frame frequencyof 60 Hz, a built-in scan driver, and a COF-mounted source driver. Thethickness of the display panel was smaller than or equal to 100 μm.

The fabricated display panel was fixed to the inner or outer surface ofa plastic columnar support member. Two kinds of display devices eachincluding a ring-shaped display region were fabricated.

FIG. 41A is a photograph of the fabricated display device includingthree bonded display panels (display panels 100 a, 100 b, and 100 c)whose display surfaces face inward. FIG. 41A is a photograph of thedisplay device seen from the above. FIG. 41B is a photograph in whichFIG. 41A is partly enlarged.

Each display panel 100 is bonded with a plurality of FPCs 104 which isconnected to a driving device. The FPCs 104 are bonded on the long sideof the display panels.

FIG. 41A is a photograph which was taken when slant stripes weredisplayed on each of the three display panels in synchronization witheach other. As shown, the display device was able to display aring-shaped seamless image along the inner curved surface of thecylinder.

Each display panel 100 includes the region 110 transmitting visiblelight and adjacent to the display region. In an overlapping part betweentwo display panels, the region 110 of one display panel which isdisposed on the display surface side overlaps with a display region ofthe other display panel which is disposed on the side opposite to thedisplay surface side. FIG. 41B shows the region 110 a of the displaypanel 100 a overlaps with part of the display region 101 b of thedisplay panel 100 b. As shown, a seamless image can be displayed at thejoint between the two display panels.

FIG. 41C is a photograph of a display device in which a single displaypanel 100 is fixed on the outer surface of a cylindrical support member.

In FIG. 41C, the region 110 transmitting visible light of the displaypanel 100 overlaps with part of the display region 101.

As in the photograph of FIG. 41C, which was taken when vertical stripeswere displayed, the display device was able to display a ring-shapedseamless image along the outer curved surface of the cylinder.

As described above, it was confirmed that the display device of oneembodiment of the present invention, in which a single or a plurality ofdisplay panels forms a ring so that a region transmitting visible lightand adjacent to a display region of a display panel overlaps with partof the display region, was able to display ring-shaped seamless images.

This application is based on Japanese Patent Application serial No.2015-009453 filed with Japan Patent Office on Jan. 21, 2015 and JapanesePatent Application serial No. 2015-040295 filed with Japan Patent Officeon Mar. 2, 2015, the entire contents of which are hereby incorporated byreference.

What is claimed is:
 1. A display device comprising: a display panel,wherein the display panel comprises a display region and alight-transmitting region adjacent to the display region, wherein thedisplay panel is flexible, wherein the display panel is curved to form aring so that the light-transmitting region at one end of the displaypanel overlaps with a display surface side of the display region,wherein the display device is in the form of a cylinder, and wherein thedisplay surface side of the display region faces inward.
 2. The displaydevice according to claim 1, wherein a ring-shaped seamless image isdisplayed on the display region along a curved surface of the cylinder.3. The display device according to claim 1, wherein the display panelfurther comprises a light-blocking region adjacent to the displayregion.
 4. The display device according to claim 3, wherein thelight-blocking region comprises a flexible printed circuit and a drivercircuit.
 5. The display device according to claim 1, wherein the displayregion comprises an organic electroluminescent element.
 6. The displaydevice according to claim 1, wherein the light-transmitting region isprovided along a first long side and a first short side adjacent to thefirst long side of the display panel.
 7. A display device comprising: afirst display panel; and a second display panel, wherein the firstdisplay panel comprises a first display region and a firstlight-transmitting region adjacent to the first display region, whereinthe second display panel comprises a second display region and a secondlight-transmitting region adjacent to the second display region, whereinthe first display panel and the second display panel are flexible,wherein the first display panel and the second display panel are joinedto form a ring so that the first light-transmitting region at one end ofthe first display panel overlaps with a display surface side of thesecond display region and the second light-transmitting region at oneend of the second display panel overlaps with a display surface side ofthe first display region, wherein the display device is in the form of acylinder, and wherein the display surface side of the first displayregion and the display surface side of the second display region faceinward.
 8. The display device according to claim 7, wherein aring-shaped seamless image is displayed on the first display region andthe second display region along a curved surface of the cylinder.
 9. Thedisplay device according to claim 7, wherein the first display panelfurther comprises a first light-blocking region adjacent to the firstdisplay region.
 10. The display device according to claim 9, wherein thefirst light-blocking region comprises a flexible printed circuit and adriver circuit.
 11. The display device according to claim 7, wherein thefirst display region comprises an organic electroluminescent element.12. The display device according to claim 7, wherein the firstlight-transmitting region is provided along a first long side and afirst short side adjacent to the first long side of the first displaypanel.
 13. A display device comprising: a first display panel to an n-thdisplay panel, where n is an integer of more than 2, wherein the firstdisplay panel comprises a first display region and a firstlight-transmitting region adjacent to the first display region, whereina second display panel comprises a second display region and a secondlight-transmitting region adjacent to the second display region, whereinthe n-th display panel comprises an n-th display region and an n-thlight-transmitting region adjacent to the n-th display region, whereinthe first display panel to the n-th display panel are flexible, whereinthe first display panel to the n-th display panel are joined to form aring so that the first light-transmitting region at one end of the firstdisplay panel overlaps with a display surface side of the second displayregion and the n-th light-transmitting region at one end of the n-thdisplay panel overlaps with a display surface side of the first displayregion, wherein the display device is in the form of a cylinder, andwherein each display surface of the first display panel to the n-thdisplay panel faces inward.
 14. The display device according to claim13, wherein a ring-shaped seamless image is displayed on the firstdisplay region and the second display region along a curved surface ofthe cylinder.
 15. The display device according to claim 13, wherein thefirst display panel further comprises a first light-blocking regionadjacent to the first display region.
 16. The display device accordingto claim 15, wherein the first light-blocking region comprises aflexible printed circuit and a driver circuit.
 17. The display deviceaccording to claim 13, wherein the first display region comprises anorganic electroluminescent element.
 18. The display device according toclaim 13, wherein the first light-transmitting region is provided alonga first long side and a first short side adjacent to the first long sideof the first display panel.